‘June 1968,’ said Cooper. ‘They were dismantling at the end of an exercise. Three observers on a shift, as usual. The young man who died was Jimmy Hind.’

Fry had brought a drink of water to her desk. Archives made her mouth feel dry, even when they were digital. She could practically feel the dust on the back of her throat. But it was such a relief to be back at work properly. She felt much more at ease now, restored to her own environment, with Cooper back in his chair, head bent over a file. Enough socializing for now.

‘The other two people involved were . . . ?’ she said.

‘The first was Leslie Michael Clay – he was leading observer, the number one in charge of the post during the shift.’

‘Leslie Michael Clay? But that can’t be the same Clay we’re looking for. He’d be well into his eighties by now.’

‘Our Michael Clay is fifty-one. He would have been too young in 1968.’

‘This was probably his father then, do you think?’

‘Could be,’ said Cooper. ‘Then there was the number two observer. Jimmy Hind’s friend, Peter Massey.’

‘Your farmer at Rough Side Farm. Go on.’

‘At the end of an exercise, the crew had to take down and dismantle all the equipment. The smaller items they took home with them for safe-keeping, but the larger bits of equipment were stored inside the post. When the accident happened, Clay and Massey were lowering the siren down the shaft, and it seems they hadn’t tied a very good knot. Hind was underneath it, waiting to position it at the bottom of the shaft.’

For a moment, they both studied the photograph of the post crew. Jimmy Hind was identifiable from the newspaper pictures. A slight young man in round, wire-rimmed glasses, with long hair sticking out from under his beret.

‘It was reported at the inquest that Clay was a lot bigger and stronger than Massey, so maybe there wasn’t an equal strain on the rope, but they could never be sure exactly what went wrong. Anyway, when it was halfway down, the siren bumped off the side of the shaft, and a knot slipped loose. Hind might have tried to dodge – there was a sort of toilet cubicle just behind him. But he didn’t make it. The siren hit Hind on the head, cracked his skull open. He went down, and the siren broke both his legs when it fell on him.’

‘And he was killed outright?’

‘Not outright. He lived on for a couple of weeks, before they turned off his life support.’

‘How old was Jimmy Hind again?’ asked Fry.

‘Seventeen.’

‘All his life ahead of him.’

Cooper nodded. ‘That’s what the coroner said, too.’

Fry looked at the printouts Cooper had gathered. She had the impression that he, too, was glad to be back at work. Since they’d both returned from Longstone Moor, their eyes had hardly met – the reports they’d unearthed had taken all their attention. With luck, some of the things they’d talked about today would never be mentioned again.