The large garden had once been a place of delight with gorgeous flowers and a little summerhouse. Like gardens up and down the land, it was now a rather forlorn-looking vegetable patch with dust, mud, nettles. And, of course, the ubiquitous Anderson shelter – a sunken semi-cylinder of zinc-coated corrugated steel – which no longer served any purpose other than as a playhouse for Johnny. There was, however, a rather mossy old teak table and chairs, where they now sat. And the day was pleasantly warm with late-summer sun.

‘So what now, Eaton?’

‘To start with, you and I are going to Godmanchester.’

‘That doesn’t tell me much.’

‘I couldn’t tell you about it indoors. It’s our most closely guarded secret, you see. Godmanchester is where it all started, Tom. It’s where we learnt that Hitler is likely to be in the Alps – southern Bavaria or the Austrian Tyrol. We had been looking for him beforehand, ever since VE Day, of course, but this was the first serious inkling we had of a location.’

‘Godmanchester is a little town twenty miles or so from here. What on earth has that to do with Hitler or the Alps?’

‘You won’t have heard of Operation Epsilon?’

‘No.’

‘And nor should you have. It’s top secret. Highest level.’

‘Tell me more.’

‘There’s a large old house in Godmanchester, name of Farm Hall. At the moment it’s a bit like a rest home or country hotel, with only ten guests – each one of them a brilliant German scientist. Actually, “guests” isn’t quite the correct word. “Prisoners” would be more appropriate, because however comfortable their accommodation might be, they aren’t checking out any time soon.’

Lydia arrived with the tea and Eaton stopped talking.

‘Don’t let me interrupt you, Philip,’ she said, placing the tray on the table.

‘If I could include you in this, Lydia my dear, I would.’

‘You boys carry on with your whispering.’ She smiled sweetly at them both. ‘I’ll go and play with Johnny – at least there’ll be some rather more adult conversation with him.’

When she was out of earshot, Eaton threw Wilde a meaningful glance. ‘It does seem to me, Tom, that your delightful wife is even more fiery than usual.’

‘Like the rest of us, she was hoping that the war was over. Despite what you might think, she was actually rather glad to have her husband back. Anyway, we’re not here to discuss my domestic woes. Tell me about these ten scientists and their relevance to Adolf Hitler’s whereabouts.’

‘Specifically, they’re all particle physicists.’

‘Ah, the atom bomb.’

‘Indeed. Until recently the bomb was the best kept secret among the Allies. Anyway, Hiroshima and Nagasaki has changed everything. Now the whole world knows about it.’

‘I’m failing to see what this has to do with finding Hitler.’

‘Bear with me, Tom. What no one in the West knew was how far the Nazis had got with their own attempts to develop the A-bomb – and what, if anything, we could learn from them. That’s where Farm Hall comes in. Among the guests being held there, we have some big and important names: Otto Hahn, for instance – the man who discovered fission. Werner Heisenberg, Paul Harteck, Max von Laue, Kurt Diebner. They are all brilliant men and they have been there since early July – nearly two months. And do you know what? We have been listening to every word they have uttered since they arrived.’