‘We’re becoming victims of our own success, chaps. The navy is pestering us to develop direction finding for their ships, the RAF want it installed in every one of their planes and the army want us to make the kit portable so they can drive it around to bolster coastal defences. And as I’m sure you’re all very aware, there are still many weaknesses in our basic systems. The magic eye is still far from magical. Our masts are not clever at detecting low-flying craft, and we’re still picking up signals reflected off tall buildings inland, which is damned unhelpful to say the very least. We’re not here to identify East Anglia’s many medieval churches, ancient and impressive though they may be. Perhaps most urgent of all, our system still can’t distinguish between friendly planes and enemy craft, which will leave us in a right fix when the buggers come a-visiting.

‘So if you thought you were going to be able to rest on your laurels now the RAF are here, you’d be very wrong,’ he went on, tamping tobacco into his pipe. ‘The work is going to be even harder, and more urgent, than before. We’re recruiting more specialists and will divide you into new teams, each tasked with a specific set of problems. As ever, you may exchange information between your groups, but you will never, repeat never, discuss it with anyone else – not even the officers or the training lot. Is that clear?’

That very afternoon Vic found himself in a room with Johnnie and another scientist called Scott, whom he did not know well, along with a couple of electrical engineers. They were obviously the foundation of a team, but no one had any idea what they would be working on. So it was a little alarming to discover that their leader was none other than Dr A. P. Rowe, a senior scientist with the Air Ministry and close ally to Watson-Watt, as the joint ‘fathers’ of the venture. If he was heading their work, it must be a very important project indeed.

Dr Rowe had a reputation for being terrifyingly stern, and they all stood nervously to attention as he entered the room. ‘Oh for heaven’s sake, sit down, chaps. No standing on ceremony here,’ he said. ‘And before any of you start trying to address me as Doctor anything, the name’s Jimmy. And who are you? Tell me your names and what you’ve been working on so far.’

He turned to Vic with a gaze like powerful headlights. ‘Okay, you first. Let’s have it.’

‘My name’s Vikram Mackensie, sir, but everyone here calls me Mac. I was doing a doctorate in radio waves at Cambridge when the boss – I mean, Mr Watson-Watt – recruited me.’ As he spoke he felt, for a brief moment, as though he were standing outside himself, observing a stranger. Is this really me? All these things I’m saying, did we really do all of this?

The feeling of unreality, of being in a dream, only intensified as the doctor – Vic could no more imagine himself addressing this titan as ‘Jimmy’ than he could calling the boss ‘Robert’ – began to describe the work they would be doing: the most important job on the station, he called it. It was a project called ‘Identification, Friend or Foe’, or IFF, which would involve developing and testing a bit of kit that could reflect or transmit a signal clear enough for the operator to interpret accurately and identify what kind of aircraft they were detecting. It would have to be small enough to fit in any kind of craft, and of course it must be failsafe.