Gilbey nodded. Now he knew why he’d been summoned and after their encounter at the Whitehall reception, it was no great surprise. Lord Swalcliffe – first name Edward, surname he couldn’t quite recall, but the man was originally from Luxembourg and he seemed to remember the name had an unfortunate Germanic edge to it – was Churchill’s principal scientific adviser and seemed to have the ear of the Prime Minister in a way few of his other confidantes did.

‘Winston is distressed at the degree of rancour existing between the various departments, agencies and individuals with whom we work. I realise that to an extent he encourages it: he realises disagreement can sometimes lead to honest opinions being expressed, which he sees as being better than suppressing one’s views. He doesn’t like matters being bottled up, like in some miserable marriage. Swalcliffe is very good at…’ Pearson hesitated, searching for the precise word, ‘distilling differing opinions and coming up with clear and concise advice, which is why this report’ – this time he held up the dark green folder and waved it in Gilbey’s direction – ‘has caused such a fuss. Lord Swalcliffe’s consistent and considered opinion has been that there is no threat from German long-range rockets: he does not think they’re feasible. That is the advice he has been giving Winston. Now you send in a report saying the contrary. He tore a strip off me last night and instructed me to sort it. So we’re going to go from here into a secure room in the basement and thrash it out. Swalcliffe will be there, of course, plus Air Vice Marshal Frank Hamilton of RAF intelligence and one of his chaps, and Long from the Ministry.’

Pearson hauled his considerable frame up from his chair and gestured to Gilbey to do the same. He paused by the door to regain his breath, turning to Gilbey and gripping him by the elbow.

‘Don’t let Swalcliffe rile you, and certainly don’t underestimate him, Tom. People do that at their peril. He’s terribly bright and misses nothing. He tends to take a contrarian view: he’s an original thinker, and Winston likes that. As difficult as he can be, he’s right far more often than he’s wrong. Best not forget that.’

There were six of them in a room that would have been a tight squeeze for four. It was more of an interview room than one suitable for a meeting. Given that all the attendees bar Pearson had been caught in the rain, there was an unpleasant fug about it. No sooner had the soundproof door been closed from the outside with some degree of ceremony than Lord Swalcliffe started speaking, dispensing with any need for introductions.