Cooper let out a long breath. ‘Ah. Tenure. That explains everything. You’ve only got a year left, at most. And you don’t want to go back into uniform. Gavin, you’re getting desperate.’

‘Do you find the idea of me being promoted to sergeant inconceivable?’

‘Well, yes.’

‘Thanks a lot.’

Cooper laughed, then instantly felt guilty – not for laughing at Gavin, but because it didn’t seem right that he should have something to laugh about right now.

They both looked up as Diane Fry came into the room. Her face was dark with irritation.

‘Hey up,’ said Murfin quietly. ‘Are we in for another go at boosting morale?’

‘Shh. You’ll just wind up her again,’ said Cooper.

‘Well, these team-building exercises are wearing me down, Ben. I’m getting emotionally exhausted from all the love I feel for my colleagues.’

Fry approached Cooper immediately. ‘Ben, the DI says he’s given you the name of some old professor to talk to.’

‘Yes. I’m hoping to see him this afternoon.’

‘When you get back, have a word with me, will you? I need to make a judgement on whether he might be of use in another enquiry. So I’ll be interested in your opinion of him.’

‘You’re not usually very keen on outside experts, Diane,’ said Cooper.

‘Personally, I wouldn’t touch him with a bargepole. But I need a reason to justify my decision not to use him. Follow?’

‘You want me to come back and tell you he’s useless, right?’

‘Frankly, I expect you to come back and tell me he’s some barmy retired academic who drinks too much and has long hair, a smelly dog and holes in his cardigan, but likes to be visited by nice young police officers. Anything like that will do.’

As Fry walked off, Murfin pointed at a page in his sergeant’s crammer, marked with a yellow Post-it. ‘“A supervisory officer should always be prepared to justify any decision,”’ he said. ‘See – I could do that.’

‘Hey,’ said Cooper, ‘if you’ve been raiding the reference library, did you happen to see that big dictionary?’

‘It’s on the shelf over there.’

‘Thanks.’

Cooper lifted the book down and flicked through the pages. There it was – Thanatology: The scientific study of death and the phenomena and practices relating to it. From the Greek Thanatos, meaning death.

Lovely. His professor was the genuine Dr Death.