The trap was fixed into position with a chain and metal stake, and a band of spring steel was anchored to the base at one end. Fry walked over to see what was happening as Cooper pointed to the steel plate at the other end.

‘See, only the trigger plate is galvanized,’ he said. ‘That needs to be thin to keep its weight down. And the catch is made from brass to prevent it rusting to the foot plate. But everything else is rusted over. That’s just the way you want it.’

‘How do you know so much about traps?’ asked Fry. ‘They’re illegal, aren’t they?’

Cooper shrugged. ‘You learn this kind of thing by osmosis when you grow up in the countryside.’

‘So you understand how it works?’

‘It’s very simple. To set the trap, you compress this spring, which allows the jaws to open, and a catch closes over them. When you release the spring again, the upward pressure of the jaws holds the trigger plate in position, see? An animal comes along and steps on the plate, releasing the catch. The spring snaps the jaws shut on its leg. The whole thing happens in about a twentieth of a second.’

Fry flinched. ‘It’s barbaric.’

‘That’s why it’s illegal.’

‘Obviously, that doesn’t stop people using them. How does an animal get out of the trap?’

‘It doesn’t. Once the jaws close, they’re locked in position by the collar. They can’t just be forced open – you have to depress the spring again. Animals don’t know that, and they’re not physically capable of it anyway. That’s why they sometimes end up chewing their own legs off to escape.’

‘I don’t suppose there’s any way of identifying the owner of this thing?’

But Cooper shook his head. ‘There might be fingerprints, I suppose. But this is quite an old trap. See – it has a bow spring. That type tends to lose its springiness when it’s left set for long periods, or if it gets too corroded. Trap manufacturers dropped it years ago in favour of coil springs.’

He hunted on the ground until he found a stick.

‘What are you doing?’ asked Fry.

‘Setting the trap off. It’ll be safer. Somebody is bound to get their hand in it, otherwise.’

Cooper pressed on the trigger plate with the end of the stick. Instantly the jaws snapped shut, biting deep into the wood and shredding the bark.

‘Jesus,’ said Fry.

Though Cooper tugged on the stick again, the trap stayed firmly attached to the ground.

‘Nice, isn’t it? And now your prey is helpless, all you have to do is come along at your convenience and finish it off. The trap was probably left by a farmer or gamekeeper with a fox problem.’

Fry nodded, accepting the explanation. But Cooper looked again at his shredded stick and the size of the trap.