The corridor eventually led them to a single cavernous room, lights strobing from recesses halfway up its bare stone walls. There was a bar in one corner, a few tables on a raised platform, and a long ledge down one side of the room where most of the clubbers seemed content to sit. The dance floor was only half full, with what looked like students keen to get the night started.

‘It’s still early,’ Clarke explained to Fox.

‘Wonder if they’ve put a cap on the capacity.’

‘If you catch COVID, I promise I’ll do your shopping.’

‘In that case, drinks are on me.’

‘I’ll stick to orange juice.’

‘You sure?’

She nodded and took the only empty table, looking around. There was no sign of any DJ, so she craned her neck and noticed a minstrels’ gallery immediately above her. It faced the bar but couldn’t really be seen from where she sat, so she got up again, slipped her mask on, and joined Fox in the queue. Now she had a better view of the upstairs. Behind a waist-high glass panel there was a long table arrayed with boxes and flashing lights, and behind it all stood Gaby Mackenzie, shoulders hunched as she listened to her headphones, fingers busy teeing up the next track. It looked as if her main aid was a small silver notebook computer, though she also rifled through some CDs, pausing to sip from a plastic beaker with a fixed straw.

‘When does the actual music start?’ Fox asked from behind his mask, handing Clarke her drink. His seemed to be identical. He nodded towards the tables, but Clarke squeezed herself into a space on the ledge, leaving him with no option but to stand in front of her. As they removed their masks, she gestured over his shoulder and he turned, clocking Gaby Mackenzie and giving a nod of under­standing.

When the next tune arrived, Clarke recognised it from the first few notes: Boards of Canada. It quickly morphed into something else, however, as the DJ added her own elements. A rapper joined the fray, appearing seamlessly. Clarke was quietly impressed. When she looked up at the gallery again, Mackenzie acknowledged her by raising her beaker.

‘We’ve been spotted,’ Clarke told Fox. He had removed his jacket and loosened the last of the three buttons on his short-sleeved shirt.

‘She’s playing your song?’

‘In a manner of speaking. You really didn’t have to come, you know.’

Fox gave a shrug. ‘Nice to have a break from the files.’

‘Anything there leap out at you so far?’

‘Just that the worst excesses – albeit unproven – I’d classify as historic, carried out by officers long retired or in some cases even deceased.’

‘I thought you might say that, since that’s the result you’re after.’