It was our fault (said Lafey, as they walked back to Finchley). Our fault, because we were the ones who left the dust in the hands of the human. My people have long monitored who travels between realms; to do this, we use a special dust to travel ourselves. We try to stop interlopers from plundering defenceless places.

The previous one of us here, the one on this world, was careless. She permitted herself to fall in love with a human. She died here, in some local trouble. I don't know what. She was supposed to have destroyed her the dust. But she didn't. Instead, she entrusted it to another human, a boy.

I don't know what she saw in him. He was clever, yes, and he was like her, like us, quick and enquiring; but he was human with all your weaknesses, arrogant and grasping. He didn't destroy the dust, but instead learnt to use it. He formed it into rings, devices that let him travel to and from the wood.

He experimented on animals, and then on children; and lastly he sent himself. We don't know what happened fully, but he somehow released the Tyrant of Charn, who we had thought safely contained; and he pulled her, the children, and another human into a realm that was just being formed.

This realm was a smaller one, and it was being directly shaped by a shard of the Emperor, named Aslan. We waited to see what Aslan's will was about these intruders. The lion found a compromise and we considered the matter closed. We do not interfere with the Emperor: we simply try and keep the peace.

But the new realm, the one you know as Narnia, was bound to your one closely in ways we didn't understand. Humans crossed without needing to go through the wood. We couldn't track how. Narnia itself was a strange place: it wasn't a full realm, like the ones that you and I come from, one of the Eleven. It was a small realm, and unusual even for one of them: inconsistent, full of rules that contradicted each other or had surprising consequences. It's one of the reasons that the time ran so quickly there, we think.

But, you humans! You came from here, and from other places like here. You flocked to it. And you did what you do: you trampled on the delicate beauty of the place with your brutish feet (although frankly there are worse things than you on other worlds in this realm; pray you don't meet them). Because of the time difference, we didn't have people there: but whenever we checked, it was the same. The humans fought the natives, and when there were none of them left, they fought each other. In the paradise of Narnia, there was always war.

You saw at least one of those conflicts. We have a fair idea about when you went back and forward, because we saw your names in the history books; although we have no idea how you travelled. Not through the wood, certainly. And we saw one thing over and again: you and your friends and family were always the bringers of change. You toppled one regime after another.

It's ironic that you complained about Aslan being late: you were worse. You never came at all. You plunged the world into chaos when you left the first time, and you didn't stop the slaughter of Cair Paravel at the hands of the Telmarines, or prevent the gnomes from being enslaved. We think what happened later in Narnia was worse, but we don't know. We probably never will.

Because eventually, inevitably, Aslan called time on it all. On the same day of the train crash that killed your family, at the exact same time, Narnia was detached from all reality. It's gone. It, and everything and everyone in it, Aslan included. The timing can't be a coincidence: we think that either the crash triggered something or Aslan used it to pull your family and friends back.

It's an anniversary, did you know that? It's two hundred thousand Narnian years since the end. Two hundred millennia is a long time by anyone's standards. Deep magic always has times associated with it, contracts that expire, debts that must be paid. And the deep magic that made Narnia was very, very strange.

And now shadows are appearing. Ghosts of old Narnia. We don't know where they came from, what they are, or how they are travelling, but they all have one thing in common: they are looking for you, Susan. They want you to do what Pevensies do: they want you to fix Narnia.

Susan was silent as Lafey spoke, and then for some time afterwards. Lafey was her usual tense self, glancing at everything they passed: she briefly stopped, stared hard at a tree, and then hurried on.

I wish she would take that kind of care when she crossed the road, thought Susan, glumly, as yet again Lafey suddenly lurched over the street, and a car slammed its brakes on and beeped at her.

The truth was that Susan had known some of this, or at least had figured it out after the events. Narnia had always felt like a strange and beautiful playground for children: and then suddenly people in that playground died. No: were killed. In bloody war. Having it spelt out so baldly, as Lafey gesticulated and frothed, just drove the point home harder.

She could feel tears welling up as she remembered the deaths: trees tearing humans limb from limb; a faun staggering to the ground, an arrow through its pink mouth; a horse screaming from a fatal pike wound. So much blood.

She had never understood why it hadn't affected the others. For the boys it was just stupid war games, consequence-free heroics; and Lucy, poor Lucy, she always saw the best in everyone and everything. And she was the one who fixed the wounded after the blades had done their work.

But then, Narnia had a funny hold on them while they were there. It laid soft edges on everything. It was like being drunk, or sleepy in a warm bed while the snow fell outside. Fifteen years ago, Susan had had an operation, and the gentle hand of the morphine on her mind was the closest she had ever felt to that Narnia feeling. It was only now, in the hard cold sobriety of adulthood, that she properly saw the ruin that they had lived through.

The fact that Narnia was gone shocked her, though, in a way she wasn't expecting. On top of that: her exclusion from that end was a punch in a soft place that she thought had long hardened. She'd been left out yet again, kept away from the magical place, despite its terrible cost.

She could feel emotion flooding into her that she thought she had safely walled away, locked in a box in a cellar in a fortress at the base of her mind.

That damn lion.

'You're quiet,' observed Lafey.

She didn't bother dignifying that with a reply.

There was no one from the zoo outside her house; she retrieved the key from where she had hidden it, and unlocked the door. The answer machine was quiet, so they hadn't called. Well, the RSPCA lady had said it would probably be in the afternoon. She hung up her coat. Lafey stalked in behind her, twitchy as ever.

Susan stopped, twirling her keys in her hand. There was a choice to be made here, the familiar tug of peril and adventure waiting to be followed. She remembered stepping through the wardrobe that first time, not believing Lucy's stories, on a grey afternoon like today, and then seeing the snow...

But that cost. That cost.

She wondered if she would be allowed to walk away from this.

Lafey suddenly stiffened, sprinted into the kitchen. 'Back, creature!', she screamed. 'Back! Susan, run!'

There was a commotion, something moving.

'Oh for goodness sake, Iris, it's just the donkey...', replied Susan, wearily; she followed the strange woman into her kitchen and then stopped in her tracks.

The donkey was not the problem. Well, it was, sort of; it was back in the house, and stared at the scene in front of it thoughtfully, while it chewed on a cauliflower. Directly in front of her, Iris was making hand gestures, and sparkles were forming around her as her magic took shape. Most curious of all though: on her kitchen table were two squirrels. One was huge, maybe twice as large as a normal grey squirrel; it was wearing a green waistcoat and a straw boater. The second was smaller and hiding behind the first. Scattered across the table was a deck of cards, a game interrupted; there was a tiny bag, chocolate wrappers...

'Queen Susan Pevensie!', said the larger squirrel. 'You've finally home! Don't know who your mate is, but you can stop the shiny stuff now, darling, we're not going to hurt no one.'

Susan pushed past Iris, who clicked her fingers and dissipated the magic. She walked up to her kitchen table and regarded the huge grey animal in disbelief.

'Are you...', she said, carefully, '...cockneys?'

The squirrel snorted.

'Hah! You can take the girl out of Narnia, but you can't take the Narnia our of the girl, can you? No, I'm not from Walford. I'm from just outside Beavers' Dam. We've just been here a little while. Gone a bit native, you know? What's that?'

The smaller squirrel behind him whispered something that she couldn't hear.

'What, it's not a real place? Course it is: Narnia's where we were born! Oh, Walford's not. It's from the telly. Oh well, don't expect that matters so much.'

He returned his attention to her, took his hat off and bowed deeply. 'My name's Skittlestone. This is my son. He's a bit shy, you know, never met royalty before. His name's Brian.'

'Brian?', she asked weakly.

'Yeah. Changed his name since we got here. Really likes that band, Queen. Kids, eh? What can you do?'

'I am going to make a cup of tea,' said Susan, hoping that perhaps this would give her some sort of stability in an otherwise tumultuous world.

'Oh, that's a great idea, milk and two sugars please,' said Skittlestone promptly. Then, to Lafey he continued: 'and who are you, if I may ask? You're not from round here, are you?'

Lafey ignored him and spoke directly to Susan.

'These things are dangerous. We don't know what they are or where they came from. Narnia is gone, these can't be from there. We must flee.'

'Well that's bleedin' polite, that is,' said Skittlestone. 'For your information, we did come from Narnia, thank you very much: we just chose not to stay when the lion shut up shop. Gave us all the choice, to his credit; but me and the nipper didn't fancy it. So here we are. So what's the plan? Wake the talking beasts, storm the castle, overthrow the false queen and rule the land in a golden age for a thousand years? Have to say we thought she was you at first; we gave the old girl quite a shock when we asked her! I reckon she should be easy compared to some of the other things you've faced.'

Susan placed two mugs on the table; one for her, and one for the squirrel. She sat down tiredly and shook her head.

'I'm sorry, all of you. I'm not a queen, here. I'm just a normal person. I have no idea what to do.'

The squirrel looked crestfallen for a moment; then he brightened.

'I'm sure we'll work it out. Us desperate band of heroes against the darkness! That's what happened in all the old stories, anyway. And they always worked out great! Erm, you got a smaller cup?'