‘If no one comes forward to claim him, you might want to consider stable isotope analysis, which should narrow down where he had originated from even more closely.’

Gillard nodded, recalling that a hit-and-run case that he had been involved with was partially solved by this technique. Stable isotope analysis examined the isotopes of carbon, ingested with food and drink and then trapped in hair, bones and teeth. These are cross-referenced to the geology of particular areas of the world and give a surprisingly accurate trace of exactly where a particular person lives. Only a few universities had the facilities to undertake the analysis, and it always took several weeks to produce results.

‘One other thing, Craig. I found a tumour in his liver the size of a cricket ball. Poor chap might not have known, but wouldn’t have lived long anyway.’

‘Not much comfort in that. All right, I need to get the ball rolling on the tests.’

Gillard knew that Rigby had ordered a public appeal for witnesses this evening and that would be followed up by a door-to-door. The Thames is home to hundreds, particularly in this bucolic locale. Narrowboats, houseboats and barges, as well as some glorious riverside properties. It wasn’t called the Thames Riviera for nothing. There was money here, and power. Motive, maybe. Quite a few who lived along this desirable stretch of river had heard something. A splash. Someone must have seen it.

Throughout the evening, when he had a spare moment, Gillard dipped into the evidence file as the control room collected the reports from the public. Going back to the previous evening, the first logged calls for the Tagg’s Island area had all concerned loud music that had been heard during the small hours of Saturday morning. Several residents had already called the local authority to complain about the racket and now, following the plea for information, renewed their complaints to the police. One late-night dog walker recalled seeing a white car, a BMW, parked on the bridge to Tagg’s Island a little after midnight, corroborating the witness statements from the houseboat residents Elvira Hart and Brent Kletz.

Hoskins’ work had borne fruit too. He’d found five one-way trips, and just three there-and-back-again journeys. One of those was by a BMW 7-series, the same type of car identified by several witnesses. That seemed the one to concentrate on. The detective constable had forwarded to Gillard the addresses corresponding to each car registration. They were all within five miles of the crime scene. He in turn forwarded them to PC Cottesloe, who was coordinating the door-to-door enquiry.