Vic had not slept well, his mind churning over the possible glitches they might encounter, but now all was set. They walked to the ferry with Johnnie, Dr Rowe and the others who would be observing from the seaplane base. As they waited to embark, he found himself pulled into an awkward embrace. ‘Good luck, old man,’ Johnnie said in his ear. ‘It’ll be fine. I’m certain we’ve got this thing right.’

‘You’re the one who needs the luck, going up in that contraption.’

‘It’ll be a first for me, going up in a seaplane. Shame you won’t be able to wave.’

The ferry powered out into the tide and was then drawn back by the current onto the opposite shore. Johnnie turned with a final wave and thumbs up before climbing onto the navy jeep waiting for them on the Felixstowe side.

Vic waved back, putting on a cheerful smile. They had become so close in the past few months, living and working together, being in each other’s company twenty-four hours a day, getting to know each other’s ways, even anticipating what the other would say next. They knew each other’s bedtime routine, the way they folded their clothes, cleaned their teeth, the little sounds they made in sleep. At work they found themselves having the same thoughts, and would finish the other’s sentences. He trusted Johnnie completely and felt they’d become almost two parts of a whole. It was the closest he’d been, as an adult, to having a best friend.

He shook himself. It was hardly a dangerous mission – these planes flew every day. It was just nerves. ‘C’mon, Scotty, let’s get back to work,’ he said, turning back to the gatehouse.

The Radio Receiver Room had been set up temporarily in a wooden hut in the courtyard of the stable block, in the shadow of the receiver mast. It was newly painted, and on that hot day the fumes were fierce enough to give anyone a headache, but they had to keep the door closed to prevent any interference from the transmitting masts just a few hundred yards away. Later, new reinforced concrete bunkers would be camouflaged under great mounds of earth, always damp and musty-smelling.

He seated himself at the desk with its small rectangular screen, next to the tracking table, and turned on the power. The A-Scope slowly came to life, blinking at him with its usual assortment of blurry grey and off-white blobs and lines. Scott stood to his right, next to the brown Bakelite telephone receiver fixed to the wall. Dr Rowe and two others squeezed into the space behind them.

The white-faced clock above their heads ticked loudly into a thick, heavy silence as Vic tinkered with the dials, making the final adjustments. Someone cleared their throat. More silence, more ticking. The clock hand reached the appointed hour. Eleven o’clock. There was no radio connection to the cockpit, so an engineer was tasked with reporting what he could see from the window of an office in one of the hangars. Even though it was expected, the harsh ring of the phone made everyone jump. Scott picked it up.