'1938,' he said without hesitation.

It was hard to think back that far, to remember what was going on in the world before the great shock of the war. 'That was the year Britain was trying for peace, right?'

'We call it appeasement now,' Mackie said, his face hard. 'Bloody great mistake. We should have declared war when Hitler marched into Czechoslovakia, thereby tearing up all the guarantees he'd given up to that date.'

'But Britain wasn't ready for war – was it?'

'We were in a damn sight better shape than Hitler. He couldn't have mounted a blitzkrieg. He didn't have the tanks or the trucks. Why, he only had three months' fuel! He'd placed orders for ships, for instance, that could have overwhelmed the Royal Navy a few years later. But he couldn't wait, had to move fast. His Nazi economic expansion was heading for a bust, and at court there was plotting against him, according to our spies. And that's also why he's kept on moving – it was no surprise to me when they took on Russia. Nazism is a bankrupt ideology sustained only by endless expansion and conquest. In retrospect we muffed it; we should have struck when the balance of power was at its most favourable for us. By waiting another year we gave him the chance to arm to the hilt.

'As to what would have followed if we had gone to war then, there are many uncertain factors. I can't imagine the French poking their noses much beyond the Maginot Line, for instance. But at worst it might have been a war like the close of the last show, a lot of infantry manoeuvres. And at best it could all have been over by Christmas, and that would have been that for Hitler and his crew. It certainly would not have been the catastrophic collapse in the west that we actually saw.'

But it would have been politically impossible to have gone to war then, Mary thought. She remembered the mood in Britain, and indeed America. Only twenty years since armistice, another European war was a horrible prospect, and Chamberlain had been a hero, briefly, when he produced what looked like a peace deal. But Mackie was showing a side of himself she had perceived among other Brits, especially in the military. These were a people who believed themselves destined to rule the world. Hitler had humiliated them the first time he put a tank-tread on a south coast beach. Anything to reverse that.

She asked, 'So how would you make the change?'

'Actually we haven't got that far. Not as far as you! I must sack my historians.'

But he was being cagey, and suddenly she wondered if he was lying, if he had some team of military thinkers working on this counter-history for real, just in case. Which made him as bad as the lunatics in Richborough – and as bad as herself, for she had been seduced into seriously contemplating how her Dunkirk project would work. The power implicit in the idea of the Loom was just too tempting.

He smiled. 'Well now, look – enough of the fun stuff. Tell me what you've found out about this old fossil Geoffrey, and his inventory of history-botherers.'

V

She opened her handbag and drew out a stack of papers, neatly folded. She spread these out on the pillar between them.

'Not such an old fossil. Quite an imaginative chap, our Geoffrey. Look – this is the summary table he appended to the front of his memoir.' It had been translated into modern English: 'Time's Tapestry: As mapped by myself…' 'We have a couple of versions, actually, but the earliest seems to have been written down in 1492.'

'The year Columbus sailed.'

'Yes – and as it turns out that's no coincidence. I'll come to that. The last version was found in Geoffrey's coffin, though that copy has been lost.'

'This was a man determined to speak to the future,' Mackie murmured.

'Oh, yes. He was asking for our help, actually; he wanted rid of the menace he called the Weaver". Now, look. Geoffrey has listed no less than six deflections of history, revealed to him by his researches – and, he says, deriving from his own experience. But I'm going to propose, Tom, that we neglect two of these…

She spoke of Geoffrey's account of the 'Testament of al-Hafredi', in which a strange visitor to the court of a petty Frankish duke had deflected an eighth-century Muslim invasion of France.

'And an entirely Muslim Europe,' Mackie murmured.

'Quite so.' And she described the 'Amulet of Bohemond', through which a time meddler appeared to have arranged the murder of the Mongol Khan in the thirteenth century. 'If not for that the Mongols would surely have swept on into western Europe, laying waste our cities – wrecking Europe for all time to come, as they wrecked so much of the east.'

'Good God almighty,' Mackie said. He worked at his pipe. 'So why do you say we should exclude these possibilities?'

'Because the technology seems to have been different. The Loom depends on feeding information directly into a subject's brain. But the Amulet of Bohemond was some kind of gadget that spoke" to its subjects.'

'Like a recording device. A tape or a phonograph.'

'Perhaps. Sent back to the thirteenth century.'

'All right. And this al-Hafredi?'

'He seems to have been a man who was hurled bodily across time – the man himself, not just his words.'

'Well-gosh. Hard to know what to say to that. But look here, if these cases are not to do with our Nazis and their Loom, then what are they to do with? Who else is building a time machine – the Japs?'

'I think it's stranger than that,' she said carefully. 'I can think of two possibilities. One, that these interventions come from our own future. More advanced technologies. Or, two-'

'Yes?'

'That they come from different histories. Ones that were, um, obliterated by the changes in the past. Geoffrey seems to hint that this al-Hafredi was a witness to a Muslim empire that stretched as far as Hadrian's Wall.'

'Which never came to pass in our world.'

'No. But his own history vanished, when he went back in time and blocked the Muslim expansion in France. And that left him stranded, I suppose. The last relic of a reality wiped into oblivion, into non-existence, the moment he threw himself back in time.' She said all this forcefully, hoping Tom Mackie would find it as scary a thought as she did.

'Oh my good golly gosh.' He got up and walked around in the long grass, his right hand cradling his pipe, his left slapping at his uniformed leg. 'Every so often – these extraordinary matters – speak to me, oh spirit of Mr Wells!' But he sounded more excited than appalled. 'All right. Then Geoffrey's remaining four instances, you believe, are to be dealt with.'

'I think so.' She spoke of the Prophecy of Nectovelin, which was apparently the result of meddling by Rory O'Malley, using a prototype of the Loom in Princeton before the war. And then there was the Menologium of Isolde, sent back by the Nazis at Richborough – and with Ben Kamen's name surreptitiously coded into it.

Mackie sat again. 'Well, we know all about those. And Geoffrey's two remaining cases, then -' He squinted at her document. 'The Codex of Aethelmaer". The Testament of Eadgyth". Ah. And I see that Geoffrey links them both to the destiny of Christopher Columbus.'

'That's the idea. Columbus was a significant figure, but one striking point is that Geoffrey couldn't possibly have known how significant Columbus would become – he wrote down his account in the year Columbus sailed.'

'Um. And the purpose of these deflections?'

'I'm speculating,' she said warily.

He smiled. 'Speculate away.'

'I think the Nazis have moved on from all those baroque Aryan dreams – the reversal of Hastings, the establishment of a northern empire deep in the past. They're too bruised by the war for all that. So what is the problem for the Germans right now? America, with all her resources and might. I think Trojan and Fiveash are trying to muck about with the founding of modern America – to abort it completely, or at least change history to such a degree that no entity like the modern United States could emerge. And they're doing it by meddling with Columbus.' She described the Codex of Aethelmaer. 'It's essentially a weapons programme,' she said.