Unlike the clear blue sea off the coast of Kent, or the wide rivers of opaque green that he remembered from India, the Suffolk seas were usually grey-brown, the colour of milky tea, bulging with the swell or stippled with breaking waves the locals called ‘white horses’. But on a few rare occasions, particularly at the height of summer, the sea lay flat as glass, almost pearlescent with blues and whites reflected from sky and cloud, shimmering and shifting like a mirage before your eyes.

It had been such a day during the sudden heatwave that arrived late the previous September – an ‘Indian Summer’, they called it – when he had been resting in his favourite niche contemplating the latest mathematical conundrum and heard voices below him on the beach, out of sight. Even though they were some twenty yards below him, every sound seemed to be amplified off the sea.

Some of the other chaps were partial to sea bathing. He listened with amusement as they urged each other on, and the howls of shock as they plunged into the water. However calm and beautiful, it was always bitterly cold. The shouts continued – some kind of game: he imagined piggy-back battles, trying to topple each other. A decade in male-only institutions had shown him that if there was no ball to kick around or throw, play-fights always ensued.

The splashing and laughter abated; they must now be out of the water, drying off.

He could identify some voices, including those of Frank Wilkinson and Johnnie Palmer, the older man who’d welcomed him that first day. Although not a fast mind, he had the ability to think deeply and rationally. He might say little during discussions but then, towards the very end, would come out with really sensible, considered suggestions, in a quiet voice that sometimes got lost in the hubbub of competing views. Vic’s respect for the man had grown over the months and he was irritated by the way some of the others teased him, mimicking his flat Midlands accent.

‘Christ, that was bloody freezing.’ That was Johnnie. ‘Good, though. Sharpens the mind.’

‘Could do with a bit of sharpening, Johnnie-boy, after yesterday,’ Frank said.

‘What happened yesterday?’

‘What the boss said.’

‘What did he say?’

‘That we don’t have much time and we need to hone our problem-solving; to focus more and think tangentially, those were his very words.’

‘Sounds like a contradiction in terms.’

Laughter from the others.

‘Apparently we need to do both at the same time.’

‘Like magicians?’

‘Like teacher’s pet.’

‘Pet? Who’s that?’

‘Mackensie.’

Vic’s stomach knotted painfully.

‘Whatever do you mean, pet?’

‘’Cos he always seems to have the answer. Haven’t you noticed? The boss adores him.’

‘He’s a bright lad. Sharp as a knife.’

‘Yeah, but can he be trusted?’

Vic found that he was holding his breath.

‘Are you saying you don’t trust him?’

‘Well,’ Frank’s voice lowered, but was still audible. ‘He’s not exactly one of us, if you get my gist?’