‘He had shell shock?’ queried my father, with mocking incredulity. ‘Did it make him forget his name?’

‘Whether he had shell shock or not, he’d been through hell,’ said my grandfather. ‘It’s not up to us to judge.’

‘You’re in no position to judge,’ my mother said to my dad, trying to defuse the tension with mockery. ‘America wasn’t even in the war until 1917.’

In this world, that one chance meeting, a stranger’s kindness, altered the points on Leonard’s destiny. He never spoke of it, but I know what happened: the old man (always old to Leonard) who poured him drinks at a zinc table in Paris, whose words and obviously broken heart persuaded a wavering young soldier to desert.

The choice Leonard made, the shame, the cost to his family’s respect, the necessary change of identity – this is the stuff that novels are made of; novels, whose purpose is to reconstitute our lost potential, to restore the worlds that might have been.

Do you like this Leonard less? Inevitably. But you only have to think of yourself answering the door in your pyjamas or nightdress, opening it to see the pale, panicked face of your young son wearing a stolen greatcoat over his torn uniform, desperate for money and forgiveness, glancing both ways down a wet provincial street, and you know you would have hidden him as long as necessary in an upper bedroom, and emptied every last coin from the cashbox, to see to it that he was able to start a new life somewhere, under a new name.

*

EVEN IN A MUCH LESS radical departure from the facts, there’s still bathos and awkwardness about Leonard’s resurrection. What if he’d merely survived, simply been more circumspect about the dangers – not volunteered for the sortie into No Man’s Land that, by family tradition, is how he met his end? If he had not died then, some other version of the secret books would have been fulfilled. Would it be better or worse? Our lives, separated in reality by half a century, might well have overlapped.

I imagine the ring of the brass bell above the door on Moyser Road, the shelves of paint and sandpaper. A familiar, unfamiliar face above a cash register. With a feeling of disappointment, I realise the narrow congruence of our interests. We’ve got virtually nothing in common. Perhaps we would talk about football or swimming. I understand that I don’t know him at all. I can see that other lives have depended on his, that his survival has been a boon to many people; but unless the whole tragedy of the war has been averted, the saving of Leonard seems unsatisfyingly arbitrary, more meaningless, in fact, than his death.

The fact is that Notovitch’s intervention came too late. It’s signing up in 1914 that does for him; no, it’s further back yet: it’s the accident of being born in 1897, in that unlucky cohort for whom the shot at Sarajevo waits like a terrible summons.