“You remember what I was telling you earlier about the Magi keeping secrets from each other?” They were standing on a windy hillside looking up at the dark building from the photograph. Even though it was surrounded by suburbs and University buildings there was something indescribably lonely about the hilltop. The grass was grey and sickly and what trees there were huddled close to ground in scrubby clumps and their lefless branches were festooned with ragged plastic bags.

The building squatted in the middle of all this like a large child’s toy that had been left in the garden to get mouldy and weather stained. Even in shape it was like a toy, a simplified sketch of a castle, lumpy and shapeless with four squat towers and worn down nubs of battlements. Oscar could see it wasn’t a real old castle, though - it was made of dark grey concrete and had a television aerial on the roof.

“I think this place might be one of those secrets.” Ridley walked away and peered round the corner of the building.

“I haven’t seen anything that looks like a door in, have you?”

“No,” Oscar admitted.

“I suspect the roof is probably the best bet,” she has walked back towards him and now held out her hand, “Here, take my hand.”

Oscar took hold of her hand and immediately felt himself being pulled upwards. Ridley seemed to be stepping up through the air, as if she was on some kind of invisible escalator, climbing non-existant steps but rising faster than she was stepping. Oscar found himself being pulled easily up behind her, rising up towards the top of the tower. As they drew level with the top, Oscar could see that the roof was flat and largely featureless, apart from a couple of large puddles and some odd little bumps and hollows.

Ridley stepped down onto the roof and neatly swung Oscar down after her. To Oscar’s surprise he heard a small thump and found the black cat winding itself around his legs again. He was sure that Ridley hadn’t carried it up with her, but had it just jumped all the way up here on its own?

Ridley was already pacing about the empty expanse of roof, stopping here and there to examine any odd bulges or dips. The cat set off after her, sniffing at her tracks. Oscar followed.

“It’s more of a tradition really, these days,” Ridley was saying, “But everyone does it. Even I’ve got a little garret no one knows about. It comes from the old days, before the Royal Order, when Magi kept their methods and knowledge secret - and key to keeping those things secret was keeping where you kept them secret, if you see what I mean - your laboratory, your house, your… tower. Every Magi has one - a secret tower - a place that no one else knows about, where they can come and work without being disturbed. And I suspect that this here ‘mysterious castle’ is, in fact, Maggs’ tower.”

“You mean Maggs used to live here?”

“I mean I think she probably still does, technically, it’s just that, like everything else, she’s forgotten it. But someone knows now - Hopkins must have worked out that Maggs came from York and he… they, I suppose, him and the Erl King, must have discovered that the family were…” She suddenly stopped and looked up at Oscar, “You have to know, I’m afraid, you ought to… the people in that house, they were a family, I think… I think they were Maggs’ family… you see… he killed them, Oscar, the Erl King, your… your Uncle… he killed everyone in that house. I’m sorry.”

Ridley stood, looking at him, her hands hanging by her sides, her face sad and lost. Oscar didn’t know what to think. He couldn’t quite figure it out, put it together. He tried to remember his Uncle’s face in the Great Hall, when he had tried to stop Cuddy and even later when they had unmasked him. He tried to see there the face of a madman and a murderer, but somehow he couldn’t. The face of his Uncle Rufus kept getting in the way. He just couldn’t, literally couldn’t - was not able to - believe it. The black cat wound itself round his ankles in a reassuring manner. Unable to think of anything else he could do, he walked up and took Ridley’s hand.

“We better stop him, then, shouldn’t we?”

She looked down at him, solemnly, “Yes, yes we should. Here - I think there might be something here.”

She bent down where she had been standing and tugged at a piece of pipe sticking out from the plain grey of the roof. To Oscar’s amazement a line appeared in the asphalt, then three, making three sides of a wide square. Then the side Ridley was pulling lifted up and he saw that it was a trapdoor. Ridley swung it all the way up and flung it back so that the dark entrance gaped open before them. They peered down into the shadows. Oscar could just about make out some stairs leading down out of sight. It was far darker in there than it ought to be.

“Why wasn’t it locked?” he asked.

“Magi don’t need locks,” said Ridley, grinning, “Their belongings have ways of protecting themselves. Ready?” And without waiting for an answer she stepped down into the darkness.

Inside, the steps led down into shadow. The light from the trapdoor faded far quicker than seemed normal, but Oscar realised that it was not completely dark. The walls were panelled with solid, dark wood but dotted all over them and the ceiling were small points of bluish light, each one of which was far too faint to make any difference on its own, but all together they spread a sort of dim twilight, letting them at least vaguely make out where they were going. When he looked at the lights more closely Oscar discovered that they were little bugs, something like bumblebees, crawling slowly over the walls, their bodies glowing feebly. Every so often one of them would take off and float gently and aimlessly through the air around them. The corridor was full of these wandering sparks. It was a magical place, something like waking through a teeming galaxy full of tiny dim stars, as confusing as it was illuminating. The cat seemed to find them extremely entertaining.

“Emberbees,” said Ridley, who didn’t seem quite as impressed with them as Oscar, “Not the most efficient lighting system. Wait.”

She held up her hand and stopped, cocking her head to listen. Oscar stood quite still in the deathly silence, straining to listen. His attention was caught by a picture on the wall. It was a drawing of a view of York Minster, but he could just make out, in the background, an immensely tall man leaning against a buttress with his arms folded. Oscar got the definite impression that the man was glowering out the picture right at him. Oscar jumped. From somewhere far below came the distinct sound of something being knocked over and glass smashing.

“Someone else is in here,” said Ridley, “Either that or some of the furniture isn’t too pleased to have visitors. Come on.”

Ridley snatched out her hand and grabbed an Emberbee out of the air. She passed her black rod over her closed fist, muttering something under her breath. The light leaking out from between her fingers grew stronger and warmer. She opened her hand and a fierce orange glow staggered out. It shook itself and then started off down the corridor in front of them, much brighter than before. Ridley, Oscar and the cat followed at a jog.

They trotted down the corridor to a junction. Ridley listened for a moment and then turned left. After a few moments the corridor turned right and then right again, so they were now going in exactly the opposite direction. They came to another junction. Ridley chose carefully again. The corridor seemed to go on forever - there were no doors or windows, just endless panelled corridor, lined with pictures, turning and meeting, back and forth in the shadowy, drifting dark, round and around in a bewildering maze. Ridley stopped suddenly and Oscar ran into her. This part of corridor seemed dimmer than the others - there were fewer Emberbees here.

“It’s trying to lose us, confuse us…”

“It’s working,” said Oscar. Then, suddenly, he jumped as a sharp knife of fear thrilled through him, drilling him to the spot. Ridley reached over and grabbed his arm.

“It’s him!” she hissed, “Isn’t it? It’s the Erl King!”

Oscar nodded, dumbly, suddenly feeling sick as that now familiar sense of dread that accompanied the Erl King everywhere became to seep over him. All around them the Emberbees were starting to go out and the shadows were creeping in, but Ridley ran on, heedless of the gathering darkness, and Oscar scrambled after her, suddenly panicking that she would leave him alone here in the darkness. But the little black cat came scampering up between his legs, turning to look at him as she passed, her eyes flashing in the darkness, beckoning him on.

They chased helter-skelter through the endlessly dividing corridors. It was a confusing pursuit - impossible to keep track of. Blundering through the shadows with Emberbees swirling around them, unable to concentrate because of the fear that the Erl King spread in his wake, they ran down the endless wood panelled corridors after the cat, barely aware of where they were going and what they were doing.

Suddenly Ridley pulled up sharply, but this time Oscar didn’t run into her. He had stopped in his tracks, too, frozen there by a sudden wave of panic - they were lost! They had come too far, run down into the heart of the tower and now they would never escape: it would wind its labyrinth around them, tightening its grip like a spider wrapping up its prey. They would wander forever in these dim, sparking passageways, first going mad and then fading away entirely, becoming nothing more than anxious whispers in the darkness, forever searching, never finding, eternally lost in Maggs’ castle…

Of course: Maggs! She had been behind all this, right from the beginning! She had tricked Oscar into following her, she had spurred on Thursby and Cuddy, humiliated first Ridley and then Skelton… it all made sense now. She must have faked her loss of powers, she must have been planning this all for years and years, moving all her pieces into place, master minding this great coup to finally put herself in power and crush her enemies: It was Maggs! She was the evil genius, she was the mysterious power behind it all, she was the Erl King, she was… nothing of the kind!

What on Earth was going on? How could he be thinking such things about Maggs? It was ridiculous! Oscar reached out and grabbed hold of Ridley as she stumbled along through the darkness ahead of him.

“Ridley, wait, something’s up… I’ve been thinking… mad things… about Maggs”

“It’s… it’s the Erl King… the fear…”

“No, no, you don’t understand - it’s different… this is different to before - that was other things… things I was already afraid of… this is… this is made up stuff…”

“You’re getting confused… it’s getting stronger… we’ve almost got him…”

“What if something’s got us?”

“Here!”

Before Oscar could stop her, Ridley threw herself sideways against the wall. As she hit it, a section of the panels swung away in front of her and she plunged through into the darkness beyond. Her flailing arms caught Oscar and he tripped after her, falling into the shadows.

As the Dragon pulled into York Station, huffing and growling, cross at being made to stop, Oscar was surprised to see that the station was almost completely empty. The only people he could see were a few nervous looking railway officials, watching them arrive from a high window, and a small knot of policemen standing by the main entrance.

As they got down from the train one of the police officers moved towards them.

“Glad you’re here,” he said and shook Ridley by the hand. He shot Oscar a disapproving glance but said nothing, “Don’t know how you knew, but I won’t ask what I don’t want to hear. This way…” and he waved them in the direction of the doors that other officers were now holding open for them.

Ridley glanced at Oscar with a confused expression on her face, but said nothing. The two of them got into a waiting car and soon they were racing through the twisting streets with the sirens wailing.

Like London, York seemed to have become a ghost city; the streets empty but for forlorn looking Christmas decorations, that swung, unlit, in the wind. The ancient buildings, sagging over the road with age, seemed abandoned, but, as they passed, Oscar saw curtains twitch and frightened faces peer out at them.

The car made its way out of the city and into more suburban streets. Ridley scrabbled in her pocket and pulled out the map from the White Tower. She turned it round a couple of times and squinted out of the window at the passing road names.

“Well, we definitely seem to be going in the right direction,” she said.

“But they seemed to be expecting us,” said Oscar, “What’s going on?”

“I’m not sure,” whispered Ridley, “But they seem to be impressed with us, so lets not disillusion them, eh?” and she winked conspiratorially.

The sirens stopped wailing and the car pulled up in front of an ugly suburban building that was actually two houses pushed clumsily together with an archway in the middle. The archway was currently full of police cars. The driver leaned back over the seats.

“Its the house on the left - there should be an officer on door, he’ll tell you what’s what…” he nodded towards Oscar and lowered his voice a little, “Are you sure you should be taking the boy?”

“He’ll be fine,” said Ridley and ushered Oscar out of the car.

The policeman on the door didn’t seem at all sure what was what and had to disappear inside several times to confer with his radio and the officers in the house, and sometimes both, before he would let Ridley and Oscar in.

They were met in the hall by an officer in plain clothes, who took Ridley aside and spoke to her in whispers. She turned to look at Oscar and he saw that her expression had become incredibly serious.

“Oscar,” she said, “I want you to have a look on this floor, see what you can see. I’m going to look on the first floor…” and she followed the plain-clothes officer up the stairs.

Despite all the whispering and secrecy, Oscar already had an unpleasant sensation in his stomach that made him think that he was quite happy staying down here, where there were plenty of policemen. He had a horrible suspicion that something nasty had happened upstairs, something that he wasn’t interested in seeing right now. And given that the police didn’t seem all that surprised to see him and Ridley made him suspect that the Erl King might be on exactly the same trail as they were.

He wandered through a kitchen into a sitting room, the cat following quietly at his heels. Policemen, some in uniform, and some in strange, rustling white boiler suits moved about around him. He could tell that they were looking at him but were either too busy working or too wary of these new inexplicable events to actually ask what a small boy was doing there.

He looked around - it seemed like a perfectly ordinary sitting room - a TV in one corner, a big sofa and a couple of armchairs, a coffee table, a mantelpiece with some pictures on it… Oscar looked at the photographs more closely. He walked up towards the mantelpiece, with the odd sensation that he wanted to try and keep what he had discovered secret, even though it wouldn’t mean anything to anyone else in the room. He looked around, but no one seemed to be paying at direct attention to him. He gingerly picked up one of the photographs.

“Oscar!”

Oscar jumped and turned and dropped the photograph. All the policemen in the room turned and stared at the sound of the breaking glass. Ridley stepped over to him from the door.

“He’s been here. The Erl King.” She looked drawn. Her lips were thin as though she had decided something. For a moment she was far away but then she suddenly looked down at him and put her hand on his shoulder. “We better get you out of here…”

“I know why.” Oscar bent to pick up the photo. The black cat was standing by it, watching him carefully.

“Come on - leave that - you’ll cut yourself on the glass - the police will clear it up.”

“No, I know why, why he came here - see?” Oscar lifted the photo frame up and glass fell out at his feet. The cat edged away from the falling shards. Ridley reached down and took it from him.

“Give that to me.”

“Look at it, though…”

Ridley was going to put it back on the mantelpiece but then she stopped. She turned it into the light coming through the French windows.

“My goodness…”

The photograph was of a young couple with a baby. They were standing on a hillside with another, slightly older woman. The three adults were smiling at the camera, although the baby didn’t seem all that pleased to be outside. Behind them, at the top of the hill, was a squat, black building, like some kind of castle. The older woman, standing beside the couple, was unquestionably, younger but unmistakeable, Maggs.

“Officer!” Ridley was carefully picking the picture out of the frame, flicking away little crumbs of glass. A policeman approached, warily.

“Yes, ma’am.”

“This building - in the background here - do you know what it is?”

“That, ma’am? That’s just over the top of the hill here - in the University grounds… I not entirely sure what it is, some kind of water tower, I think.”

“I thought it was some kind of substation - you know, for the electricity,” said a policeman behind them.

“It’s one of the University departments, isn’t it?” said another.

“It’s a funny thing,” said the first, “But I’ve never noticed it on any maps…”

There was a small smile on Ridley’s face. She put the photograph in her inside jacket pocket.

“Can someone drive us there, please?”

There seemed to be more policemen at St Pancras than there were passengers. The station was almost completely empty apart from the armed officers walking carefully to and fro across the concourse and in their wake the lonely travellers clustered anxiously round their bags. People spoke in whispers and seemed lost and insignificant in great, solemn space of the station.

Ridley ushered Oscar along towards the farther side of the station, past queues that were forming at the head of every platform, as people waited to have their bags searched by stern policemen. Already Oscar could see Magi, in a green uniform that he couldn’t recognise, moving down the queues, scrutinising the passengers as they passed by.

Their own destination, however, was obscured by a great billowing cloud of smoke and steam. Oscar wondered if something somewhere was on fire - black smuts started to dot his clothes and the smell of burning stung his nose as Ridley led him down the platform.

Through the thick steam he caught glimpses of colourful and ornately decorated carriages, covered all over with lots of gleaming brass fixings and delicate and mysterious patterns. All the windows were decorated too, with magical symbols cut into the glass and many of them were closed by thick green velvet curtains. Through the few that were open he could just about make out an interior full of more green velvet and gold braid.

It wasn’t a long train - only three or four carriages long - and soon the steam began to thin and Oscar could see they were approaching the engine. It was completely unlike any train engine he had ever seen, outside of old films and books. It was black and gleaming and a number of Magi in overalls that would have been practical apart from the magical patterns embroidered on them, wandered back and forth polishing and tending the machinery. Only was it machinery? Peering through the wreathing smoke, the pipes began to look like tentacles or whiskers, the metal started to look like it was made up of many iridescent scales, the whole tender seemed to swell and fall as if it were… breathing…

And then, as they approached closer, the whole of the front of the engine rose up and turned towards them: a great, bearded, shiny face, with a short, blunt muzzle, a hint of huge white teeth and two dimly glowing red eyes like warning lights. It wasn’t a steam engine at all: it was a dragon.

Oscar stood, rooted to the spot, as the Engine Dragon shook his enormous, heavy head at them and snorted steam out through nostrils like gleaming funnels. Ridley reached up and patted the Dragon’s hissing muzzle and it nudged her back with evident affection. The black cat came sauntering down the platform and sat down next the Ridley, regarding the dragon with a curiously superior expression. One of the Magi in overalls came up to them, wiping his hands on a piece of cloth and looking very pleased with himself.

“Took all six of us to conjure her back up - took five of us just to find which shed she’d been left in…” he patted the Dragon and then wiped where his hand had been.

“Its good to see her again, isn’t it girl?” Ridley scratched the Engine under the chin with her staff - it sounded like someone running a stick along a piece of corrugated iron, “Are we ready to go?”

“She’s fed and we’ve got a full head of steam up,” said the Magi Engineer, “The first full run of the Great Northern in twenty years: it’s going to be quite something.”

“Then what are we waiting for? Let’s go…” Ridley turned and started back towards the carriages.

“Right then,” said the Engineer and, with a great grin plastered on his face, he took a whistle from his pocket and blew it: “All aboard!”

Oscar sprinted after Ridley and followed her and the cat up the steps into the first carriage as all the Engineers ran up towards their special cabin just behind the Engine Dragon. Then Chief Engineer blew his whistle again and, with a great bellow and a rush of steam the Dragon sprang forward down the lines, catapulting Oscar through the door into the soft green seats of the compartment, as they leapt forward, out of the station, and away in a whirlwind of smoke and sparks and magic, away through the tunnels and between the houses, away up the lines to York.

Oscar sat back in his seat, watching the countryside rush past, as they sped up the line north. Ridley sat opposite him, on the other side of a table stacked high with tea things, including, Oscar had been pleased to discover, a large number of cakes that Ridley didn’t seem to want. There had to be some kind of spell cast on the carriage, because in here it was incredibly hard to tell that they were travelling at all, but even when the carriage did occasionally shake and rattle, the tea things were all very careful to brace themselves and make sure that nothing spilt. They weren’t being helped, though, by the black cat, who was amusing herself by chasing a particularly nervous saltcellar around the table.

“Told you it would be worth going by train, didn’t I?” said Ridley, grinning, “Only way to travel. I never thought I’d see any of the great Engine Dragons running again in my lifetime, let alone be able to commission one for my own business in broad daylight… amazing, quite amazing… You know,” She leant forward, “When I was your age they only ran them at night - and that was only in emergencies - the only time I ever got to ride in one before today was the night the Wild Ride attacked our college. That was pretty much the last time before they put them away for good.”

“This is what I don’t understand,” said Oscar, who was now full of cake and able to concentrate on less important matters, “The Magi have been around for ages, right? And I know everyone was hiding from the Erl King, but Uncle Rufus isn’t that old - I mean, you just said that there were even Dragons before then - I mean, how come no one knows about you? Someone must have noticed something…”

“Oh they did - lots of people have known or suspected, at different times - after all, Isaac Newton set up the original Brotherhood with the permission of the King - so he must have known - but the Magi have always liked to keep things secret, even from each other. It takes a lot of research and skill and training to summon spirits, you know - and before the Brotherhood was founded it was even more difficult than it is now - back then Magi were always scared of someone else finding out their tricks and stealing their spirits, so they kept everything secret and, well, old habits die hard, I suppose…”

“Maggs said something about Newton: but I still don’t really understand what he did.”

“I’m afraid that’s another one of the mysteries of the Magi, really: you see, Newton and the other founders of the Brotherhood created the Great Work, the spell that created the modern Royal Order, but how they did it was kept secret and today is lost completely…

“But I’m getting a little ahead of myself - I take it you know the story of Merlin?”

“The wizard? With King Arthur and the knights and dragons and everything?”

“Well, there weren’t really knights back then, but there were dragons, of course…” Ridley paused for a moment and looked at him, “Perhaps I’ll refresh your memory anyway…

“A long time ago, after the Romans had left Britain, but long before the Normans came, and far away to the West, there was a King called Vortigern. Vortigern was trying to build a castle to protect himself from his enemies, but each time he got it halfway built, the earth would shake and the Castle would collapse back down into a huge cloud of dust and a little pile of rubble. Then Vortigern would have the architects whipped and start all over again.

“After several tries, though, the architects were starting to get a little fed up at this arrangement, and Vortigern wasn’t too pleased, either, so he called together all the wise men and asked them what he should do to keep his Castle up. And they told him that he had to sacrifice a child with no father at the base of the tower and only then would it stay in one piece. Now, obviously, children without any kind of human father at all aren’t in plentiful supply, but fortunately for Vortigern there was one, a boy called Merlin, whose father was said to be the Devil, or perhaps a faerie, but certainly not a normal man. So Vortigern had Merlin brought to him and prepared to sacrifice him.

“Merlin, however, was not overjoyed at being killed just to keep a Castle up, and told Vortigern that his wise men were wrong, and what he had to do was dig a deep pit beneath where the castle stood. Well, Vortigern dug the pit and at the bottom they discovered a Red Dragon and a White Dragon, locked in fierce combat, and it was their buffetings and crashings that was making the ground shake and destroying the Castle…

“Now, obviously that’s just a story, and it has a more complicated ending and might mean all kinds of complicated things, but what Newton discovered was that it held a grain of truth - there are two dragons: the two most powerful spirits in Britain, spirits so powerful and so ancient that no Magi would dare even trying to capture them with magic. They simply wouldn’t know how.

“But what Newton also discovered was that there was a way to do it. The ancients had built monuments - standing stones, barrow mounds, that sort of thing - that helped them channel and use the powers of the greater spirits, but in the thousands of years since the skills had been forgotten and the new cities and castles and houses had ruined the spell.

“So Newton set about working it all out, just as he did with Mathematics and Physics, and eventually he was ready to perform ‘The Great Work’. With the help of other Magi - including a famous architect called Hawksmoor - he had constructed a system of buildings that worked as a spell, binding one of the Great Spirits: the White Dragon, placing it in the power of the Magi.

“And that Great Work became the keystone of the Brotherhood of the Magi: ensorcelling the White Dragon changed Magic forever - it put great power into the hands of the Brotherhood, power that was shared with every Magi that joined. What had been a little London club became the official body of Magic in Britain. And that power made the practise of magic easier - many other spirits bowed before the White Dragon - it meant that instead of all the research and experimentation, to command a spirit you just needed to know the right words of command:” and here she said something in a language that Oscar could almost, but not quite, understand, “and they obey you…”

As she spoke the cake stand waddled uncertainly towards Oscar and then shuffled round until the last two remaining cakes were facing him. He took one and it bowed graciously and then sidled back to its place by the teapot.

“So… I… I could do magic if I wanted?” asked Oscar.

“You’re already making crumbs appear from nowhere,” said Ridley, “Seriously though, yes, you could, you could and you will… I promise. Once all this is over…”

“You and Maggs? You’ll teach me?”

“I’d be honoured.”

And Oscar sat back, visions of whole armies of cake stands at his beck and call filling his head as he gazed rapturously out of the window and, before he knew, fell fast asleep.

Dropping right into the middle of a group of policemen, who, as one, drew guns and took aim at the pair of them. Ridley barely had time to react to this when the door to 10 Downing Street opened and Murray stumped out on his crutch, with a tight knot of more policemen and Magi behind him.

“Ah, there you are,” he grunted and then added, as an afterthought, “My Lord. They’re with us,” and he waved his crutch at the policemen surrounding them.

The scrum of police and Magi - many of whom, Oscar now noticed, were wearing a green uniform he didn’t recognise, which had silver emblems of the Knight Errant lance on the collars - parted as a fleet of limousines drew up and formed a defensive corridor between the cars and the front door, and it was somewhere in this confusion and flurry of barked orders that Oscar found himself shaking hands with the Prime Minister.

“I understand I have you to thank for my life, my boy,” the Prime Minister pumped his hand up and down and clapped him on the shoulder, “There’ll be an official statement, of course, but I can only say thank you and, well, good work.”

The effect of the honour was almost ruined a moment later when a General ruffled his hair and called him a ‘clever little fellow’, but Oscar couldn’t help grinning like an idiot as the politicians crammed past into the cars.

Cuddy came bustling up, looking very pleased himself.

“Going to the Palace,” he said, trying to make it sound as if it was something he did regularly, “Lots to do… good work you two, by the way, very nicely handled - looked very good that, Marion, springing into action like that, impressed the PM, I could tell.

“And we’re going to need more of that sort of thing - we’re public now and we have to use it, understand? We have to take up our responsibilities - the Knights Errant are going to be taking charge of the defence against the Wild Ride, but we need more than that: we need results, we need the Erl King - that’s your job now Oscar, and yours, Ridley: don’t let me down.”

And then he was gone, disappearing into a knot of policemen to be bundled into car with the Home Secretary and a very confused looking Admiral.

The cars had pulled away in a flurry of activity, pulling, in their wake, squads of Knights Errant and policemen off on desperate errands and vital missions, until Downing Street was suddenly quiet and almost empty.

Ridley and Oscar walked down towards Whitehall. Already the whole area was sealed off by policemen, but now, in the distance, Oscar could see Spirits taking up their part: statues stumping down from their plinths to take up guard positions in road junctions, Wyverns flapping blackly down to perch on streetlamps, Knight Mares clattering off to herd traffic away. And slowly the stillness of these streets was spreading out across the city as roads were closed, shops were shut, offices emptied, as the terror of the Erl King blanketed the whole of London in a quaking silence.

“So,” said Ridley, “We have our orders, then, my Lord, the trouble being, where do we start?”

“Well,” said Oscar, “I’ve been thinking about this, a bit. I’ve been thinking about Hopkins.”

“Hopkins?” Ridley was surprised, “Who on earth is Hopkins?”

“He’s man in the White Tower. I saw him in there.”

“Oh,” Ridley went quiet, “That Hopkins.”

“I know, but listen, when we were getting everyone out of the Tower he wanted to see Maggs, to tell her something, but then he wouldn’t say what it was and refused to leave the Tower.”

“So? He was mad before he went in there, if you believe the stories, he’s probably a fair bit madder now.”

“No, well, yes, but I was thinking about what the thing, the mask, said in the Museum, something about, being held prisoner in fear, you know, and it made think of the White Tower and made think of Hopkins and what he might know about Maggs.”

“And what he might know,” the light was dawning on Ridley’s face, “About the Darklings…”

They were standing the courtyard of Hopkins’ castle, but it had changed almost out of all recognition since the last time Oscar had been there. This time there were no sign of servants or soldiers, except for something in a corner that Oscar was rather afraid might be a body. There were gaping holes in the walls and miles of broken masonry all around. The courtyards was covered in piles of rubbish and discarded, broken weapons. Here and there were smouldering heaps of wood and cloth. Black and grey smoke drifted over the scene. Somewhere far away they could hear shouting and screaming and the clash of war. The ground trembled under their feet with the distant rumble of explosions.

“It wasn’t like this last time we were here,” said Oscar, “They were all parading and everything and there were walls…”

“I don’t know what’s going on,” said Ridley, “But I think we ought to get out of it - which way was it?”

They found the library, eventually, and in it they found the servant who had shown them there the last time they had visited; only this time he was hiding under a table. Ridley hauled him out and sat him down.

“What’s going on here?”

“The rebels… they attacked…”

“That’s it!” it was coming back to Oscar, “He said something about being crowned every morning and then starting a revolution every afternoon…”

“Starting a revolution? Against himself?” Ridley was confused.

“Oh, there’s always a revolution - every day,” said the servant, “Then his ineffableness puts it down and we crown him again. But this time he didn’t. It didn’t stop - they’re still fighting - so I came and hid in here. They never come in here - not ever…”

“You mean Hopkins didn’t beat his own rebellion? Hopkins is winning? I mean, Hopkins the rebel,” Ridley was starting to confuse herself

“Oh no, ma’am, no one is winning,” said the servant blithely, “Because his unbelievableness has gone, so no one’s in charge - they’re just fighting because they don’t know what else to do.”

“Hopkins has gone?”

“His Wondrousness has gone into shadow, my lady - they’ve been rebelling since then.”

“Gone into shadow? You mean the Wild Ride?”

“A darkness came and His Marvellousness went with it,” said the servant. He sounded like he wasn’t quite sure what had happened.

“Sounds like Erl King beat us to it,” said Ridley.

“They said before that he was in league with the Darklings, perhaps he’s helping them somehow.”

“My word, if he is, I think I know how, and I think I now know why the rebels never attack the library,” Ridley was looking at the bookshelves, “Look at this: Newton’s Principia Magica, Hawksmoor’s Commonplace Book, Dashwood’s Hellfire Diaries… this has got to be one of the most complete libraries of magical books I’ve ever seen…”

“I don’t understand,” Oscar was trying to extract a copy of Seven Spells of Seven Effective Magicians, which he thought sounded useful, “I mean, isn’t this prison? How could he get all these books in here?”

“Circles and moons!” Ridley clapped her hands, “That’s it, that’s why he wouldn’t leave - this is what was keeping him here - this is what the White Tower gave him - a library any Magi was dream of - every spell book ever written, even the lost ones, the ancient ones, all under one roof! He beat the White Tower! Man’s a genius…”

“I think he’s batty - rebelling against himself everyday.”

“So he’s spent his time in here researching into magic…”

“And rebelling against himself…”

“And rebelling against himself… what more could the Erl King want? The question is what do they want with Maggs?”

“The terrible work the King hath wrought shall by the King’s own hand be brought to naught.”

Ridley whirled round: “What did you just say, Oscar?”

“It’s something Maggs said - and it’s written down here,” Oscar was bending over a desk, looking at some notes that had been left lying on it. He read it out again: “‘The terrible work the King hath wrought, by the King’s own hand shall be brought to naught.’ What does it mean?”

Ridley moved to look over his shoulder.

“I’ve heard her say it myself - she always said it was the only thing she could remember from before the Wild Ride attacked her…. Stars and Spirits!” Ridley slapped her hand over her mouth, “That’s Maggs’ handwriting, I’m sure of it - these must be her notes! What else is there?”

Oscar riffled through the pages on the desk: they were all covered in strange spidery symbols and diagrams - then something recognisable jumped put at him:

“Look, a map!”

“Let me see…” Ridley laid it flat on the table between them, “…looks like a city…”

“Ork… I’ve never heard of that… is it a magical place?”

“I think that’s just the end of the name… York, perhaps? Yes, I think it is - what’s that there?”

“Looks like someone’s scribbled on it… I can’t read it though…”

“No it’s in Enochian, a magical language, but it’s in code, too, I can’t make it out… I do know one thing, though…”

“What’s that?”

“I have looked into your future, my Lord, and I foresee a long journey by train…”

“Well, John, it’s a lovely day for this group of children, as they assemble here in Downing Street, and it’ll be a lovely day for the Prime Minister, too. It’s been a difficult week in Westminster, this week, and I’m sure he’ll be glad to be dealing with schoolchildren rather than his cabinet for at least one afternoon. And here he is, with his wife and one of his own children, coming out of Number 10 now, waving the cameras as he comes to greet these children, winners of a Blue Peter competition. And who knows, perhaps some of them might be able to help him with his current troubles - all of them won their place here by suggesting new policies for children - and that’s just the sort of headline grabbing policies that the Prime Minister needs right now to distract his political opponents from…

“Hang on, wait a moment - there’s some kind of commotion in the crowd waiting and watching at the end of Downing Street - I think its some kind of demonstration - there’s some shouting - the police are moving in - there appear to be a group of people, all in some kind of uniform, pushing their through the crowd - and Special Branch are trying to get the Prime Minister back inside Number 10 - the police are trying to restrain the crowd - some of them are trying to move the children - its rapidly descending into chaos here in Downing Street… Oh my god! What’s that?…”

All at once everybody stopped shoving and shouting - a shiver ran through the crowd and they all instinctively drew back, huddling together, even before most of them had seen the long dark shape dropping from the rooftops above. One of the policemen fired his gun as the thing dropped and everyone in the crowd ducked and then stayed there, crouched down, hardly daring to look at the shapeless mound of clothing now that had fallen into the road.

Then, slowly, it began to rise, taller and taller, stretching up out of the pool of its blood red coat tails, its bone white head swinging this way and that, its long, thin fingers twitching, searching for a scent. The Erl King had come to Downing Street.

Someone in the crowd began to scream and the policeman with the gun began to fire wildly as the Erl King swept round to face him. Galvanised by the firing the crowd began to panic, everyone suddenly blundering about, still bent double, running into each other, the walls, out into the street, driven senseless by the fear the Erl King brought with him. Out in the road two police horses bucked and reared, their hooves flailing over the heads of the scurrying people.

The gun didn’t seem to worry the Erl King at all. He swayed for a moment and then darted forward, barely seeming to move at all, snatched up the policeman and flung him across the street into the abandoned cameras of the press. The moment the shooting stopped the crowd froze once more and a sudden silence descended. Someone somewhere was whimpering in a high, terrified voice.

The Erl King paused once more and then swung round slowly to face the Prime Minister, who was standing in front of the door to Number 10, surrounded by the children visiting him, desperately trying, ineffectually, to shelter them. A single long, white talon bent out to point at him and the thin, hunched figure tensed, as if about to leap…

“Stop, in the name of the Royal Order of Magi - You are under arrest!”

The Erl King swung back towards the gates as Ridley soared up over them, her black staff pointing straight down at him. Behind her the gates began to buckle and stretch, the metal bending to make a doorway through which more Magi poured. The Erl King turned and crouched as Ridley sailed over his head, coming back down to earth in front of the Prime Minister and the children. He seemed to be about to leap at her but as more Watchmen gathered around him, leaping up to occupy window ledges and rooftops, trying to cut off his means of escape, he shrank back even further, indecisive.

There was a grinding noise from out in the street, following by a metallic clattering and shrieks from the crowd as a bronze statue of someone on horseback leapt down from its podium and came ringing and sparking up towards the gate. Behind it came more statues - generals and prime ministers - waddling on their stiff metal legs: Winston Churchill clanging like a great bell as he came, his raised arms creaking into life.

The Erl King tensed and leapt and Ridley leapt too - but he was too fast. He twisted in the air and then there were two Erl Kings and then three, four - dark figures ricocheting across the narrow confines of Downing Street, bouncing from wall to wall. The Magi tried to catch them, but they were too fast, too numerous. And then one of them reached the rooftops and exploded into a flurry of black, rasping crows, and the air was full of beating wings and shining feathers and somewhere in the confusion a thin, scarlet figure fled across the rooftops and away.

Ridley dropped back down again, landing next to Oscar.

“Murray, stay here, try and get this mess in order - the rest of you, follow me - we can’t let him escape this time!” Then she turned and slipped an arm round Oscar’s waist, lifting him up, “And you, you are my good luck charm, come on!”

She turned back through the gates to Downing Street, to where the police horses had been; only now they weren’t police horses at all. For one thing they were still rearing up on their hind legs and their hides had turned a deep purple colour, but something about their legs had changed, their back legs had become thicker, stronger, so that they could happily walk on just the two of them, while the hooves on their front legs had divided up into thick, simple fingers that clacked together loudly as they moved. And they had sprouted horns from their heads, great, thick, spiralling horns which twitched and turned, swivelling round as their heads turned back and forth.

Ridley grabbed hold of the reins of one of them with her free hand, put a foot in a stirrup and swing them easily up into the saddle.

“Yales,” she explained, simply, “The traditional mount of the Knights Watchmen - Knight Mares, they used to call them…”

And with a flick of the reins, she swung the Yale about and they set off up Whitehall at a clattering lope.

It was not the most comfortable journey Oscar had ever endured. The saddle had changed shape along with the horse, but it didn’t help with the Yale’s strange, off kilter run that felt like they were constantly in danger of tipping over. But, on the other hand, galloping through the centre of London on a mythical animal is just about fun enough to make up for any discomfort.

Ahead of them a thick flock of squawking black birds wheeled and scrabbled over the roofs of the buildings, diving between streets and across open spaces. They jinked and turned in hot pursuit, the Yale swerving between buses and then leaping over the bonnet of a car in one heart-stopping rush.

They came rattling over Trafalgar square, splashing through the fountains, scattering tourists and pigeons as the sound of police sirens grew around them, then they turned sharply after the birds up a side street.

They cantered up the street, as Oscar and Ridley scanned the skies for the birds.

“There!” Oscar spotted them, flocking round a church spire in the distance.

Ridley urged the Yale on, up past Leicester Square, where the police cars were already gathering, sealing off streets, ushering people off the pavements.

They flashed past Chinatown, Oscar getting a glimpse of mouths full of food in restaurant windows, hanging open in amazement as they went past, and then they were at the church they had seen ahead of them, plunging into thick maze of smaller streets.

The flock of birds was getting thinner now, losing its numbers, getting harder to follow. Ridley turned into a wider road and then turned again, trying to catch their track.

They came out into a leafy square that had a small park in the middle of it. People scrambled out of their way as they came trotting in, jostling each other to get out of the park, while two policemen fought against the flow, trying to get in. In the commotion two or three ravens, all that was left of the flock of birds, flapped noisily up from the grass onto the roof of an odd little black and white building in the centre of the park.

“Lost him!” Ridley wheeled the Yale round, looking for something that might help them pick up the trail again.

They were alone in the park with the policemen, who, now they were finally in, looked like they wanted to get back out again and who backed away nervously as Ridley trotted up towards them, staring at the Yale’s horns in fear.

“Did you see him?” barked Ridley. The policemen stared back at her, open mouthed.

“The Erl King,” added Oscar helpfully. The policemen now stared at him, no wiser.

“The terrorist,” said Ridley. The word seemed to wake them up.

“Clear the streets,” said one of them.

“Fugitive on the loose,” added the other, as if glad to be saying something that sounded like it made sense, “Armed and dangerous.”

“Do not approach,” added the first one with a kind of satisfied finality.

“Absolutely,” said Ridley, “I think that would be a very good idea,” and she turned the Yale away from them, back across the park.

“Do you think he was deliberately trying to confuse us?” asked Oscar.

“Almost certainly,” said Ridley, grimly, “There’ll be Magi scattered all over London now…”

“But someone’s bound to find him, then.”

“Unless…” Ridley suddenly sat up straight in the saddle, alert, “Unless that’s his plan: like the Museum, distracting us, splitting us up, so he can attack us where we least expect!”

She wheeled them round and urged the Yale forward, out through the gate to the park and down a side street towards the main road. They came cantering out from between two tall buildings and Oscar suddenly realised that they were right outside the White Tower. The police were already there in force, with cars pulled across all the roads, blocking all directions off.

The Yale bucked and wrenched round, balking at the flashing lights, as policemen ducked and ran from them. Ridley pulled hard on the reins, pulling them round and the Yale leapt up, bouncing over the roof of a police car and down the other side into the empty road.

Almost immediately sirens started up behind them as they went careering down the road at full tilt, and Oscar could hear the complaining of tires from somewhere behind. Ahead of them was another junction, with more cars blocking it off and this time with policemen running forward, trying to stop them.

A police car came squealing out of a side street, fish-tailing to a screeching stop as they swerved round it and then they were leaping and dodging between policemen and parked cars as Ridley tried to get them through the cordon.

The Yale leapt another car and then slipped on landing, it hooves scrabbling for purchase on the tarmac. Thrown this way and that, Oscar suddenly found himself pulled out of the saddle as Ridley jumped clear of the beast. The Yale scrambled upright again, whirling this way and that, scattering policemen, as Ridley ran for a side street, still carrying Oscar.

“No time for all this…” she gasped, but Oscar couldn’t see how she hoped to out run all these policemen while carrying him.

Then she grabbed hold of a lamp post as they ran past and they sprang outwards and upwards: she kicked off against a wall and then bounced off a window sill, a cornice, and suddenly they were up on the roofs of London and running, bounding, leaping along between the chimneys.

Ridley swung Oscar round, onto her back, and he clung on for dear life as she leapt across a narrow alley and went sliding across the wide roof of a theatre, then a single, suspended, breathless moment as they arced out over a wide street in one long jump, a thump, a landing, a run and another leap, the empty air around them unnaturally silent.

Then they were back among the roofs and the turrets and the chimneys, careening down tiles, then catching hold of a balustrade to swing out and across to a flagpole, the sudden rustle of leaves in the roof garden and gravel underfoot, then slipping across a sloping glass roof to a wide, flat area where they dodged between aerials and pipes to a higher roof beyond.

The roof of London was an extraordinary place. As he bounced along, Oscar felt that he was seeing somehow behind the scenes, places that only pigeons ever visited, lonely gargoyles that no one ever noticed, deserted floors of buildings with weeds growing in them, odd little wells and courtyards with no doors to them, a view of the city that few ever got to see.

Even the famous sights were unrecognisable from up here, they leapt at you, unsuspected, the unnervingly empty Trafalgar Square, the broad run of the top of Admiralty Arch, the leads of Whitehall, and then there they were, dropping once more into the chaos of Downing Street.