In an age of electronic policing, there was also much to be said for meeting colleagues from other squads and other divisions face to face whenever the opportunity presented itself. Loath as the likes of Cairns would be to call it that, it was a valuable exercise in networking. It meant you didn’t just pass on little discrete quanta of information pertaining only to specific inquiries, like worker ants meeting in a line. And perhaps most importantly, it was more conducive to a little quid pro quo. When Cairns had goodies to hand over, he liked to sound you out for what might be available in return.

‘Glad to see you’re feeling better,’ Catherine told him, having ordered up a couple of coffees. ‘When I heard Bob Cairns had called in sick, I thought it was one of the signs of the end of days.’

Cairns looked quizzical for a moment, then realised what she was on about.

‘Naw, I’m fine. It wasnae a health thing: more a kind of family emergency. My youngest had a problem with her digs. She’s at uni in Preston, starting final year. She stayed on over the summer doing a research project. Anyway, the wee place she’s in is right by the river, which is lovely until the fuckin’ thing bursts its banks. Ground floor is under two feet of water noo.’

He took a mouthful of tea. Catherine noticed him eyeing his phone as he did so.

‘You expecting a call?’

He rolled his eyes as if to say ‘and how’. He wasn’t for giving anything away yet, though.

‘Heard you had the bold Abercorn trying to peek at your homework over the Jai McDiarmid murder,’ he said. ‘Have you worked out his angle?’

‘I’m wary of even thinking so,’ she replied. ‘It’s often when you reckon you’ve worked out Abercorn’s angle that he’s got you exactly where he wants you.’

It was a calculatedly neutral reply. Catherine wasn’t giving away to anybody that she suspected Abercorn was protecting Frankie Callahan, and certainly not to a stalwart of the Drug Squad. Never mind Abercorn’s angle, she wondered: what’s yours, Bob, and what are you hoping I’ll toss back in return for this morning’s tip?