Mackie whispered, 'Mary. Old English. Speak to Egilsson. Make him hear you through Eadgyth.'

'Yes… Egilsson. Orm Egilsson. Hierst pu me? Bist pu??r? Bist pu??r, Orm Egilsson? Orm Egilsson! Hlyston ond mune, for pon ic pu recce. Hlyston ond mune, ond giefst to pin sunum ond to hira sunum…'

EPILOGUE

'My son didn't deserve this, George.'

'I know, Mary, I know.'

'To be killed by practically the last shot of the conflict.'

'Oh, the war's not over yet, Mary. And, look – well – he's with my Hilda now. His Hilda. That's something, isn't it?'

'Do you really believe that?'

'I was brought up to believe it. And, you know, I think if I try really hard I can believe it again.'

'Well, you're going to have to teach me.'

'Mary – George – please.'

'Tom? What now?'

'I know you don't want me around. But I have to show you this…'

If he could hear their voices, Ben knew he must be waking. If he was waking, he had been asleep.

And if he had been asleep, he must have implemented another of Julia's grisly historical changes. He had died and had been reborn. Again. That deep fear stabbed at him. It was a fear at the transience of life, at the impermanence of it, the fragility. A fear like being suspended over a thousand-foot cliff.

He put it aside, and kept his eyes closed. Sleep hovered about him, a loose blanket. Perhaps if he willed it he could bring it back, fall away from the world again.

But if he slept again, could he control his dreams?

'Mary. Look. These are your own notes – look, your transcription of Eadgyth's testament, taken from Geoffrey's memoir, written out in your own hand. Can you see?'

'It's changed. It no longer reads as it did. Send the Dove west! O, send him west!" West, not east.'

'History has shivered around us, Mary. The past has changed.'

'And yet we remember.'

'And yet, yes. It may take a century of tinkering with this Loom of Trojan's, and even more theorising, before we understand any of this…'

Ben had a good memory. He always had. It had only been enhanced by Julia's hypnotism and the mnemonic tapes. He thought he could remember every word of the time-manipulating chunks of doggerel she had beaten into his head, every one of the attempts she had made to change history. Even the 'dry runs', as she had called them.

And Mary's Dunkirk counter-history had intrigued him. He'd had plenty of time to think this over, lying in his tank.

What might have happened if, for some reason, the Germans had not pressed home their advantage in the spring of 1940, and had allowed the BEF to survive? There would have been a ripple of changes, he had concluded in the end, a chain of different decisions on both sides. People would have died. Of course they would. Ben knew the Nazis. If they could not conquer a slice of England, they would have struck at it another way – with terror, probably, with bombs on London and the other cities, a blitzkrieg against civilians. People would have died. But not the same people. Not Hilda Tanner, for instance.

And, perhaps, not Gary Wooler. Gary who had kept his promise to save Ben, Gary who would not have had to grieve over a young wife butchered by a Nazi thug. And he, Ben, would not have had to lie in this absurd glass box and listen to Gary being shot dead, his life unlived. Gary whom Ben had always loved above anybody else. All he had to do was fall asleep, and dream of an eccentric astrologer at Hitler's court. If he did that Gary might be spared all that pain.

He could do this, Ben Kamen, the helpless boy in the box, who had been used and abused by all of them. Even now he could save them all, and himself. Perhaps he could create a tapestry of time with a little less blood on it, a little less Weltschmertz, a world with a little less sorrow. Even though he would have to die, once again, to do it.

'You know, Mary, if we could find a way to control this technology – I mean, to compute and moderate the effects on history correctly – perhaps we can exploit it to make limited, controlled changes. I'm still drawn by my scenario of the 1938 war. If we were to implement that, all of this suffering could be avoided-'

'No. Listen to yourself, Tom! We must stop this now. Demolish this monstrous thing, this Loom. Why, it's what Geoffrey Cotesford begged us to do in his memoir. I mean, even if you could be sure your change was pure, your motives just – what happens when somebody else gets hold of this technology? Stalin, another Hitler? What then?'

'Um. I suppose you're right. We'll let the sappers take it apart, and the man from IBM can have the Colossus.'

'Are you serious? Do you promise me?

'Of course. Just as soon as the medicos get Ben Kamen out of this glass box.'

'Speaking of whom-'

'Yes, George?'

'Is Ben smiling?'

The boy slept beside the calculating engine.

And then-

Afterword

Possible alternate outcomes of Dunkirk have been analysed by, for example, Andrew Roberts in his essay in Virtual History, ed. Niall Ferguson (Picador, 1997). Panzer General Heinz Guderian (in his book Panzer Leader, 1952) said he believed the order to hold back at Dunkirk was a mistake, and that 'only a capture of the BEF… could have created the conditions necessary for a successful German invasion of Britain'.

Hitler's planning for 'Operation Sea Lion', the invasion of Britain, was recorded in German archives and has been well documented, not least by Churchill himself in Their Finest Hour, the second volume of his monumental six-volume history of the war (Cassell, 1949), and by Peter Fleming in Invasion 1940 (Rupert Hart-Davis, 1957). More recently Derek Robinson's Invasion, 1940 (Constable, 2005) focuses on the importance of naval power in the defence of Britain.

The first speculative accounts of a successful Nazi invasion of Britain appeared during the Second World War, for example the novel When the Bells Rang by Anthony Armstrong and Bruce Graeme (Harrap 1943). Norman Longmate's IfBritain Had Fallen (Hutchinson 1972) is a careful account of a successful invasion. Richard Cox's Operation Sea Lion (Thornton Cox, 1974), based on a war game played out by veterans from both sides, post-predicted a German failure. More recent studies include Martin Marix Evans' Invasion! Operation Sea Lion 1940 (Pearson, 2004).

Sir Samuel Hoare, ambassador to Spain in 1940, had been a favoured candidate of Hitler's to take over as Prime Minister had Britain fallen (see Hitler's Table Talk, ed. Hugh Trevor-Roper (1953)). Himmler's SS did establish lebensborn Aryan breeding camps in the occupied territories, notably in Norway. A recent reference on Nazi science and pseudo-science is The Master Plan: Himmler's Scholars and the Holocaust by Heather Pringle (Fourth Estate, 2006).

A useful reference on conditions in wartime Britain is Wartime Britain 1939-1945 by Juliet Gardiner (Headline, 2004). A recent reference on the German occupation of France (my model for some of the portrayal of 'Albion' here) is Richard Vinen's The Unfree French (Allen Lane, 2006). My sources on prisoner-of-war camps included P.R. Reid's Colditz books, particularly The Latter Days at Colditz (Hodder amp; Stoughton, 1953). The Germans had a habit of referring to their British enemies as 'the English', and I have reflected that here.

Kurt Godel's speculations on the nature of time in rotating universes were published as 'An Example of a New Type of Cosmological Solutions of Einstein's Field Equations of Gravitation' in Reviews of Modern Physics vol. 21, pp447-50 (1949), and the philosophical implications explored in 'A Remark about the Relationship between Relativity Theory and Idealistic Philosophy', in Albert Einstein: Philosopher-Scientist, ed. P.A. Schilpp (La Salle, Illinois, 1949). In a recent review of Godel's work and his relationship with Einstein, Palle Yourgrau argues passionately that the implications of Godel's insights have yet to be fully assimilated by the scientific and philosophical establishment (see A World Without Time, Basic Books, 2005).