In a typically impassioned farewell speech, he’d said: ‘I cannot adequately put into words my admiration for you all. I brought you together – a motley bunch of brilliant brains here in this beautiful, magical place – but I had no real idea whether we could make this thing work. You have exceeded my expectations, more than I could ever have wished for. So while I leave you with a heavy heart, be assured that in my new role I will be fighting your cause to ensure that this work continues with more funding, more manpower, more recognition. For I firmly believe that our project will become one of the most important defences of our country, our culture and our lives. And without you, it would never have happened.’

Dr Rowe, who’d taken his place, was an altogether tougher kind of chief: more exacting, more controlling, and much less inclined to encourage the kind of wacky ideas that sometimes led to exciting developments.

A trio of stern-faced navy men had arrived earlier that morning, their uniforms glittering with braid, and had been cloistered with the new boss for a full hour. What could they have been talking about all this time? It was such a simple piece of kit, and they’d drilled no more than eight small fixing points in the fuselage. The tensions of the wires had all been checked and approved by navy engineers. How could it possibly have affected the flight so catastrophically?

At last, the heavy oak door opened. ‘Come in, gentlemen,’ Dr Rowe said.

The dreaded interrogation was, in the end, mercifully brief. They examined the diagrams that had been agreed with the naval engineers, including the fixing points for the dipole wires and the exact size of the holes they were allowed to drill. Vic described the plan for the day: three flights would be made at three, ten and then twenty miles out, passing Bawdsey to the north and then flying southwards towards Harwich. Nothing was said or asked about the purpose of the trials, or where Vic and Scott had been when the plane went down. Nothing was said or asked about Johnnie, almost as though he’d never been there.

‘Got off lightly, didn’t we?’ Scott muttered as they went to find a cup of tea.

‘We’ll see,’ was all Vic would allow. ‘I can’t understand why they went so easy on us.’

Half an hour later, when he was full of tea and cake and just beginning to wind down, there was a tap on his shoulder. ‘Dr Rowe would like to see you in his office at five,’ the secretary said.

‘All of us?’

‘Just you, Mr Mackensie.’ His heart plummeted.

‘What does the old man want now?’ Scott said.

‘My guts for garters, probably.’

He’d been expecting this moment, the ‘I think it’s best if we let you go back to your studies in Cambridge’ moment, ever since the crash. As the remaining leader of this disastrous trial, it was only right, and the letter of resignation was in his inside pocket. He was ready for it – had even started to imagine himself back in the lab, cycling to his digs, walking the quads – and perhaps it would be for the best, since there was so much more development to be done to make their system workable, and he could not imagine continuing to lead the team without Johnnie.