Gillard was awoken at two a.m. on Thursday by a call from the Met Police liaison unit which specialised in dealing with California’s tech giants. Apple had come good, and had forwarded a dynamic trace of Kelvin Arrowsmith’s smartwatch. He got out of bed and dressed rapidly, with a rising sense of excitement. This was a quicker result than he had expected. On a couple of previous occasions, when seeking the contents of messages on encrypted platforms, he had discovered that a court order had to be filed in the relevant district in the US.

A phone wasn’t the ideal way to examine a map, but it showed enough detail to make it clear that the smartwatch had travelled from Arrowsmith’s home to the vicinity of Rissington Common in the first two hours after his abduction. Then the signal went dead. That could be good news. If Arrowsmith was being held inside a building, the chances were that GPS satellite signal would not get through. Likewise, it could be bad news. If they’d killed him and buried the body, you’d get no signal either. The other option was that the abductors had discovered the watch, realised its significance and destroyed it.

Michelle Tsu was covering the nightshift at Mount Browne, and he messaged to ask her to maximise the map and pinpoint the exact location where the last signal was received. He would be at Mount Browne in half an hour, and they would rope in a couple of patrol cars to head down to the village. He reminded her to copy in Thames Valley Police.

He was already in the car when Michelle rang him. Answering on the hands-free, he listened as she described the last location as being in a field close to the river. ‘It’s pretty much where the first body was discovered,’ she said.

‘I don’t want you thinking about a second body, Michelle. Be optimistic. He might still be alive.’ As he rang off, he heard her mutter: ‘And pigs might fly.’

By the time he arrived at Mount Browne, Michelle was already in the car park talking to uniformed officers from the two patrol cars that were going to take them to the site. Gillard remembered to remove his grab bag of wellingtons and torch from the boot of the Vauxhall before they set off.