Cooper could tell that Headon pronounced the word ‘bomb’ with a capital ‘B’ this time, and he knew immediately what he meant.

‘The atomic bomb.’

‘That’s the baby. Believe it or not, Ben, when you were a child, me and my mates in the Royal Observer Corps were your first line of defence against a nuclear holocaust. That was the time we went underground.’

FRY KNOCKED ON the door of the DI’s office. She was feeling very pleased with herself. Almost smug, some might have said.

‘Get any more out of Naomi Widdowson?’ asked Hitchens.

‘No,’ said Fry. ‘She’s gone “no comment”, like her boyfriend.’

The DI looked at her. ‘But there’s something else. I can tell from your face, Diane.’

‘I decided to get the calls record from the phone network,’ she said.

‘But we already did that. Irvine and Hurst went through all the calls on both of Patrick Rawson’s phones, didn’t they?’

‘Yes.’

‘The only calls we couldn’t identify were to a pay-as-you-go mobile. And that was the one Naomi Widdowson used to set up the false deal.’

‘That’s right.’

‘So?’

Fry shook her head. ‘I didn’t mean Patrick Rawson’s phone records, sir. I meant Deborah’s.’

‘What – Deborah Rawson’s?’

And Fry finally allowed herself to smile. ‘Luckily for us, some people have no idea how to cover up a crime.’

ON THE EDGE of the hill, Cooper was able to look back at the town of Edendale, constrained in its hollow by the hills to the north and the sharp cliffs of the edges to the east. The pressure of housing demand might force Edendale to expand some time, if national park planning regulations allowed it. He could foresee a day when those houses would gradually push southwards into the limestone of the White Peak.

‘It wasn’t a popular idea, going underground.’

‘I can imagine.’

‘But it was inevitable. There’s not much point finding yourself standing on a brick tower with a pair of binoculars in your hand when a nuclear bomb goes off.’

Cooper nodded, keeping his eyes on the road. He had David Headon and his friend Keith Falconer in his car, and they were heading out of Edendale, driving west until they’d left the houses behind and there were only the cat’s-eyes in the road and the light rain that drifted across his bonnet.

‘That’s what we were reduced to by then,’ said Headon. ‘Modern aircraft had developed until they were much too fast for us. So it became a question of reporting the size and direction of a blast, monitoring the fallout, observing a nuclear attack without putting yourself in harm’s way. That could only be done underground. It was all very different.’

To Cooper, that sounded like a massive understatement. Watching your world destroyed around you was different from anything he could imagine. But Headon and Falconer talked about it all so calmly, in such a matter-of-fact tone, that they might have been discussing a new type of lawnmower, or the arrival of wheelie bins.