Gillard was always glad to speak to the Home Office forensic pathologist. On every cadaver he cut through to demonstrable fact, separating assumption from observation.

‘I’ve had a quick look at the chappie,’ he said. ‘My report won’t be ready for a couple of days. But here’s what you need to know to begin your other enquiries.’

Gillard reached for a notepad. ‘Go ahead.’

‘The deceased was probably mid-fifties or so, and seems to be of East Asian origin. Chinese, Japanese, Korean perhaps. In my opinion he had already been dead for several hours before he found his way into the River Thames.’

‘What about those impressions on the body?’

‘I’ll get to that. First things first. What I can tell you for certain is that he didn’t drown – there was no evidence of significant liquid in the lungs, nor of the characteristic foam that one gets in the airways. The cause of death was almost certainly compressive asphyxia.’

‘You mean he suffocated?’

‘Yes, a particular form of suffocation. He simply couldn’t expand his lungs enough to breathe. The symptoms were quite clear, indeed spectacular: profuse petechiae in the conjunctiva and strong cyanosis in the head and neck. Pressure on the thorax was sufficiently intense to reverse the blood flow in some important veins and arteries, some of which can be seen in the upper body. There was also a distended jugular vein in the neck, which again would be caused by excessive pressure. Those conclusions are reinforced by evidence of damage to the body. A broken collarbone, two cracked and one detached rib, plus extensive evidence of bruising on the thorax.’

‘Did the netting cause that, do you think?’

‘Hold on. I think you’re jumping to conclusions, Craig. Let’s disentangle, if we may, those two observations. We cannot automatically assume the marks on the body were connected with the cause of death.’ Delahaye’s habitual caution was informed by knowing that any conclusion needed firm forensic foundations. They might have to be defended under the most rigorous cross-examination.

‘Sorry, David.’

‘Let’s start with what the body is telling us. Compressive asphyxia. The best-known examples were those in the Hillsborough disaster, fans crowded against others for several minutes. The only case I have personally dealt with was in Southwark in 1993. An arrested youth dying when a large police officer knelt on his chest, making inhalation impossible. It usually takes some minutes to kill this way. There are numerous high-profile arrest death cases from the U.S. The literature is extensive. However, although I haven’t yet had chance to review it, I have to say at the outset that the trauma to the body appears to be so severe that I suspect it is beyond human agency.’

‘You mean an accident?’