Everyone clapped. ‘Good for you, Mac,’ Frank whispered, with a new tone of respect.

Told you so, Johnnie said.

There was no time to change his mind; they had to go at once, before the onshore breeze built up. The engineer, who everyone referred to as Sparky, was a gruff, weather-beaten fellow with a rolled-up cigarette permanently attached to his lower lip. When the jeep stopped at the base of one of the masts, Vic looked up in utter terror. The metal structure appeared flimsier than he’d imagined, not much more robust than the Meccano he used to play with, and so tall it seemed to scrape the clouds. Rising through the centre was a spindly metal ladder protected only by widely spaced hoops.

‘Blimey,’ he breathed. ‘Are you sure you really need me up there?’

‘Don’t worry, laddie. You’re young and fit,’ Sparky said. ‘It’s only three hundred and sixty feet.’ The numbers meant nothing until they began to climb, reaching the first stage, where two great platforms the size of tennis courts reached out like wings on either side of the mast.

‘Sixty feet,’ Sparky announced, as Vic struggled for breath. Only sixty feet? They were still just one sixth of the way there. At the next stop, two hundred feet, he began to feel seriously wobbly. His lungs were hurting and his fingers cramped from gripping the narrow metal rungs of the ladder. The wind that had been barely detectable down on the ground now buffeted them like a gale. He clasped an upright spar with both hands as though his life depended on it.

‘Don’t look down, mate. Just enjoy the view.’

It was certainly a magnificent sight, enough to distract him for a few moments. To the south, the River Deben glittered before them; the town of Felixstowe was bounded in the distance by the silver band of the River Orwell, and the docks of Harwich on its further side. It was the sight a German bomber might see, if it managed to penetrate their air defences.

They reached the top at last. Vic’s lungs were hurting as he gasped for air – was it thinner up here? – and his heart thumped so fast he feared he might collapse.

‘It’s just your mind playing tricks, laddie. The fear. But it’s no more dangerous up here than at sixty feet. If you fell, the result’d be the same.’

‘Thanks for the encouragement.’

Battling against the wind, they inspected the transmission kit together. At first they could find nothing wrong, until Vic noticed that the calibration of the meter was slightly out, which then required a slight adjustment to the direction of the aerial.

‘Hope that works,’ he shouted.

‘If it don’t, we’ll be up here again tomorrow,’ Sparky retorted with a wry smile.

The downward climb was, if anything, even more terrifying, because he had to look at his feet to make sure they were securely on the next rung of the ladder, which made his head spin with vertigo. When at last they reached the ground, his legs were so wobbly that Sparky had to support him to the jeep.