Finally, they crossed a small ridge and found themselves at the foot of Peter’s Stone – Gibbet Rock, as Tom Jarvis had called it. Cooper wondered if Anthony Lingard had been gibbeted on top of the outcrop, or from the side of the rock itself. Or perhaps from the slope below it? There was nothing to indicate which.

On this side of the rock, there was a scree slope, an unstable mass of tiny, loose stones. Scree was notoriously difficult to climb, so a path had been worn towards the eastern side, where the gradient was steeper but more stable underfoot. Cooper looked up at the limestone outcrop. It was full of nooks and crevices.

They were breathing heavily by the time they had scrambled to the top of the outcrop. Cooper helped Fry up the last stretch, and stopped to get his breath back. From here, there was only one farmhouse visible on the skyline further down the dale. The opposite slope was formed of limestone terraces and more scree. Lumps of stone dislodged by the sheep lay around it like giant hailstones.

A few minutes later, Cooper lay half-hidden between two rocks, his head down in a deep crevice. He began to inch back towards the air, and when he emerged, he was clutching something in one hand.

‘What have you got there?’ asked Fry.

Cooper was panting, and red in the face from the blood rushing to his head while he was upside down.

‘Well, it looks like a Tupperware box,’ he said. ‘It was tucked away out of sight in this fissure. And there’s something inside it, see –’

‘Let’s have a look.’

The box was about nine inches long, with a tight yellow lid. It wasn’t actually Tupperware but something similar, made of tough translucent plastic. It had two handles that hinged on to the lid and held it in place, making the box pretty much airtight and waterproof. It had been hidden deep in the crevice, and concealed from casual view by a lump of limestone. Fry brushed off some dirt and eased open the lid.

‘Lord, what’s all that junk?’ she said.

Cooper leaned over her shoulder. Among a lot of other stuff in the box, he glimpsed a small toy dog, an England badge, a set of coloured crayons and a pair of sunglasses. There was even a Matchbox Land Rover Freelander that he would have loved as a child.

‘I can see a notebook, too,’ he said, reaching to lift the crayons out of the way.

Fry held up a hand. ‘Get it back to the office and let scenes of crime go through everything. If he’s left us a clue here, we don’t want to miss it.’

‘We’ve got an appointment,’ Cooper reminded her.

‘Yes, I know.’

Fry looked at her hand and sniffed her fingers, checking for traces of sheep droppings.