‘That’s how he dropped the weight,’ Mallory said.

There was one left. Whitestone pinned a portrait of an intense, unsmiling man to Mallory’s wall. He was posing for some kind of company photograph and he considered the camera with eyes that looked black.

‘Salman Khan,’ Whitestone said. ‘From a wealthy Anglo-Indian family. Builders, funnily enough, defying all the racial stereotypes. His father made a pile building estates in the sixties and seventies. Khan has also known the King brothers and Philips since prep school. Works as a human rights lawyer in the London offices of Butterfield, Hunt and West. Considered one of the rising stars of the legal profession. Successfully sued the Ministry of Defence on behalf of disabled servicemen.’

‘You mentioned a conviction of assault for Ned King,’ Mallory said. ‘Anything else on their records?’

‘Adam Jones had multiple convictions for drug offences and vagrancy. Six months after the school picture was taken, he was expelled for selling controlled substances behind the tuck shop. Pills. Dope. And plenty of it.’

‘The upper class are always a greater mix than they are given credit for,’ Mallory noted. ‘What was he doing? Supplementing his personal use with some dealing?’

‘Looks like it, sir. Adam went off the rails early. He was getting into heroin when the others were getting into Oxford, Sandhurst and Goldman Sachs.’

‘DC Wolfe, was Jones expelled from the Royal Academy of Music for dealing?’

‘No, sir,’ I said. ‘Not for dealing. He was smacked out of his brain during an Albinoni concert in Duke Hall. Nodded off during the adagio.’

‘Don’t you hate it when that happens?’ said Gane.

‘Our two victims,’ Mallory said. ‘They were both living dangerously, weren’t they? One had a long-term commitment to opiates. The other was a violent, serial philanderer. Either one of those lifestyles would shorten life expectancy.’

He left the rest unsaid, but it hung in the air: their lifestyle choices did nothing to explain their identically butchered throats.

I looked down at a slim red volume I had before me. Get Tough! How to Win in Hand-to-Hand Fighting – As Taught to the British Commandos and the U.S. Armed Forces. The author was Captain W. E. Fairbairn, co-inventor of the commando knife. On its front was a drawing of two grappling soldiers. It looked like some old-fashioned Boy’s Own-style comic. But inside was a manifesto for murder. I had placed a yellow Post-it note on the page I wanted, the one where they taught you how to execute the carotid thrust.

Artery #3. Knife in right hand, edges parallel to the ground, seize opponent around the neck from behind with your left arm, pulling his head to the left. Thrust point well in; then cut sideways. See Fig. C.