He was trembling so much it seemed at first he might have fired at the ceiling after all, but as they all rushed forward, he collapsed in a heap on what was clearly an expensive rug from somewhere exotic. The bullet had blown a large hole just by his ear, and blood was pouring onto the rug.

Hendrie knelt down beside him, and Tindall’s eyes swivelled towards him, apparently in recognition.

‘Who did you tell, Tindall – who are you working for?’ Gilbey sounded nervous now; he kept repeating the question.

Hendrie held Tindall’s wrist, feeling for a pulse. ‘He’s gone, sir. We shall never know.’

Two nights later, a drinks reception was held in Whitehall for some American Gilbey had never heard of but who was deemed important enough for a three-line whip: all invitees will attend, with the Prime Minister’s name used as bait.

These Whitehall receptions were like poisoned chalices in more ways than one, a reminder of how hard it was to know who to trust and an often tiresome exercise in who to avoid.

Tonight was a case in point: Gilbey had found an agreeably dark corner where he had a good view of the gathering and which was also on the route the waiters took from the bar back into the room. He’d seen off some American general with more stars on his shoulder than he imagined was legal when Lord Swalcliffe appeared in front of him.

‘What’s this I hear, Gilbey?’

No greeting, no pleasantries, no small talk from Churchill’s scientific adviser. A boxer throwing an uppercut straight from the bell: typical Swalcliffe.

‘I have absolutely no idea, Lord Swalcliffe.’ He noticed Swalcliffe didn’t have a drink in his hand, which wasn’t promising.

‘I hear…’ Swalcliffe paused, looked round and moved closer – far too close for Gilbey’s liking. ‘I hear you’ve been asking questions about rockets: German ones.’

‘I ask questions about lots of matters, Lord Swalcliffe. It’s part of my job.’ Gilbey could have kicked himself. It was a poor response, feeble and defensive.

‘Not in this case it isn’t. Forget rockets. Good evening.’

Chapter 3

England, October–November 1942

Tom Gilbey was furious, his shouting echoing along the corridor and possibly on the floors above and below his office. In his opinion it was bad enough – even inconsiderate – that Llewellyn Tindall had killed himself before they could interrogate him. But far worse was the other man in the flat – the one Tindall had been seen talking to off St Martin’s Lane – somehow managing to escape. That was inexcusable.