‘Well, it’s different, of course,’ said Cooper, ‘if you happen to live in a caravan.’

If he could have seen over the next hill, he might have been able to make out the red blob of a similar phone box in Bonsall Dale. That was the one Rose Shepherd had made two calls to. According to the map, it must be the nearest one to Lea Farm, where Simcho Nikolov had lived. Calls to the phone box by prior arrangement. Miss Shepherd had been in contact with Nikolov in the past three weeks.

Their connection supported speculation in the Bulgarian intelligence reports, a theory that Nikolov and Savova had been friends, or even lovers. Here was a link that had been more difficult to break than a mere business relationship.

Well, it was handy that rural phone boxes were marked on Ordnance Survey maps. But the box wasn’t what Cooper had noticed first. His eye had been drawn to the contour lines showing the steepness of the slope and the footpath above the bridge. It was funny the way things worked out sometimes.

He was turning to tell Kotsev that they might as well go back down to the burnt-out car, when two shots echoed across the hillside, one following quickly after the other. The flat smack of the first discharge sent birds scattering from the trees.

Kotsev looked around anxiously, and his hand went to his hip. ‘It’s stupid not to be armed. Why don’t they let you have guns?’

‘We don’t need them,’ said Cooper. ‘Most of the time.’

‘And the times when you do?’

‘We try to keep out of the way of the bullets.’

Kotsev snorted. ‘It’s stupid. You know this is the only police service in the world whose officers aren’t armed?’

‘No, there’s New Zealand too.’

‘New Zealand? But all they have to deal with are kangaroos. Here, you have armed gangsters, and terrorists. The IRA. Yardies. al-Qaeda. It’s stupid.’

Cooper laughed, and Kotsev glared at him.

‘Why are you laughing?’

‘I think you just don’t understand us, Georgi.’

There was a movement in the field ahead, and two figures appeared, walking rapidly down from the direction of the phone box. When they passed a stretch of fallen wall, the figures became identifiable as two men wearing peaked caps and quilted body warmers. Both of them had double-barrelled shotguns tucked under their arms.

‘So,’ said Kotsev. ‘Do we run away?’