‘That’s fantastic cyanosis,’ said Rainy, pointing to the purple stain visible across the face, neck and upper chest. ‘The guy is almost incandescent. It’s like he’s a wee toothpaste tube and all the blood got squeezed to the top.’ Rainy had been a junior doctor in Glasgow for several years before finally throwing in the – presumably bloodstained – towel in search of something a little less stressful and with significantly shorter hours. The fact that she chose to become a police officer caused some of her colleagues to question her judgement, but in the six months she had been with the Surrey force, she had proved diligent, intelligent and marinated in the same kind of dark humour as theirs, required to get through the worst shifts.

‘What does the pathologist say, sir?’ Hoskins asked.

‘I’m waiting for his call. It may be hours yet.’ Gillard looked up at the clock.

‘Well, I’m no pathologist, but I’d say this wee fella was asphyxiated. He didnae drown.’

The two other detectives stared at her.

‘Och, I’m just gassing, sir. But when I was training in Glasgow we had an exam question about the Ibrox disaster back in 1971. Sixty-six dead, crushed when a terrace collapsed. I saw the photos. I was only twenty-one. You dinnae forget them in a hurry. Some of them looked a bit like this.’

Gillard pursed his lips. ‘Okay, that’s interesting. Any ideas, Carl?’

Hoskins inclined his head, and said: ‘Could it be, sir, that this is some kind of industrial accident involving an illegal immigrant? The body being dumped, simply because that’s the most convenient way to be rid of him without any awkward questions being asked by the authorities.’ Hoskins was shaven-headed and overweight, with a weakness for the stodgier offerings at Mount Browne’s cafeteria. Consistently underestimated by colleagues, his diligence on the boring hours of CCTV checking, the bedrock of modern detective work, was valued by Gillard. It more than balanced out the off-colour jokes he was prone to letting slip.

‘It’s entirely possible, Carl. As I say, we’ve had no one report him missing, which might well indicate he was here illegally.’

‘So what’s the next step, boss?’ Rainy asked.

‘I’ve got an underwater search team looking around both Tagg’s Island and Ash Island, to see if we’ve missed anything in the water, particularly netting. They are also going to check if there are any industrial water intakes nearby on the river, anything industrial that might be connected to this.’

‘What about us?’ Carl asked.

‘We need to speak to the witnesses again,’ Gillard said. ‘There seem to be some inconsistencies. Rainy, I’d like you to follow up on the public appeal this evening, and feed back useful information to the officers going door-to-door. Carl, I want you to look at the ANPR.’