He rang off and found another ten-pence piece, then took from his pocket the card Harry had given him. He had begun to feel a kind of strange elation at having cheated death. In fact, he felt more alive than he had done in months, perhaps even years. He dialled the number, ready to taunt whoever answered, but heard only a continuous whine from the receiver. He tried again, with the same result. Disconnected.

Had they cleared out then? Or changed the number when they had decided Hepton must die? There didn’t seem any other explanation as to why Harry would have given him the card. Unless … He studied it more closely. Thick card, inflexible, covered in a plastic coating. Quite a robust thing, really, given that all it contained was a telephone number, and a discontinued one at that. He asked the attendant if he possessed such a thing as a knife. The man looked dubious, but they went to the shop, where he found a Swiss Army knife. The rep was whistling cheerily, selecting a dozen or so chocolate bars before moving on to the sparse display of music cassettes. Hepton chose the thinnest blade on the knife and began to cut along the edge of the card, the attendant watching, unsure what to expect. The rep came over too, his selections made.

The plastic was tough, but once he was through it, Hepton noticed that the card itself was very thin, more like paper. He began to peel it off, revealing a thin piece of metal studded with solder.

‘What is it?’ asked the rep, intrigued now.

‘It’s a PCB,’ Hepton answered, quite calmly.

‘A what?’ asked the attendant.

‘A printed circuit board. Smallest one I think I’ve seen.’

There could be no doubting that it was a transmitter of sorts. Crude, as something this size needed to be, but probably effective. Hepton smiled, shaking his head. No need to check your car’s wheel arches these days for an unwieldy magnetised box; something the size of a business card would do the job every bit as well.

‘Can I pay for these?’ the rep asked the attendant and, show over, the attendant nodded, taking back his knife and going behind the counter. Hepton stood beside the rep, waiting his turn to pay for petrol.

‘I’d like a receipt too, please,’ the rep said to the attendant as Hepton held the transmitter between forefinger and thumb and gently, surreptitiously, slipped it into the man’s jacket pocket. He held his breath, then stepped away. But the rep hadn’t noticed anything, and with any luck he would continue all the way to Leeds still in blissful ignorance.

‘Have a good trip,’ Hepton called to him as the man went out to his car. Then, having paid for the tankful of petrol, he went out to his own vehicle, started it and headed off in the opposite direction, whistling.