She closed the door without making a sound and we turned to look at Salman Khan. He was staring at us with open belligerence. You see that kind of aggression in poorly socialised dogs, I thought. They don’t bark because they are angry. They bark because they are afraid.

He ranted for a minute or so. We let him get it out of his system. A big part of our job was talking to people who were scared. Scared of getting in trouble. Scared of getting hurt. Scared of getting more hurt than they were already. But I had never seen a man quite as scared as Salman Khan. He looked like a man who was scared of having his throat cut.

When Khan paused to catch his breath, Mallory introduced us in his mild-mannered way, and we both showed our warrant cards. Khan slumped back down in his big leather swivel chair as we took a seat opposite him, Mallory making reassuring noises about various leads being pursued while I watched Khan fiddle with an unlit cigarette in his hand. The offices of the law firm Butterfield, Hunt and West were non-smoking, but there was a silver cigarette case on Khan’s desk. He worried the cigarette in his fingers like a set of rosary beads.

‘We realise this is a traumatic time, Mr Khan,’ Mallory said.

‘You shouldn’t be talking to me,’ Khan said, placing the cigarette in its silver coffin. ‘You should be out there finding the killer.’

‘Why do you think someone wanted to kill Hugo Buck and Adam Jones, Mr Khan?’

‘Because they were addicts,’ Khan said. ‘One of them was a sex addict and the other was a drug addict. Hugo was a dear friend. Adam – I hadn’t seen Adam since leaving school. But they were both, in their own way, hopeless addicts. And that’s what killed them.’

It was a credible theory on the surface. One man was a sexual adventurer and the other was a junkie. They were the victims of random murders, acts as senseless and irrational as most murders. Very sad and all that, but they were living dangerously and they died because they had it coming.

But the theory did not explain Khan’s naked terror.

‘You knew both men for many years,’ Mallory prompted. ‘Since you were at school.’