All the same, he slipped his warrant card under the glass shield of the security desk with the same unease he always felt arriving at any prison. He waited while the serious-looking woman on the other side, who was neither pleasant nor unpleasant, studied his identity, before shoving the small grey tray containing his warrant card back at him. ‘Please put your phone and any valuables in one of the lockers behind you, Detective Superintendent.’ She gave him only the very faintest nod of acknowledgement that they were both on the same side here.

Roy complied, immediately feeling naked as he parted with his ID and phone – his lifeline to the outside world – set the combination and stepped through the electric door, which immediately closed behind him like an airlock.

Tabloid newspapers regularly ran shouty headlines about how cushy life inside British prisons was. But he bet none of their editors had ever sampled even just one night at Her Majesty’s Pleasure.

He hadn’t either, but he’d talked to plenty of people who had. And no one, ever, had told him it had been a party. In many prisons, such as Sussex’s Category B, HMP Lewes, on some wings the inmates were forced to share a cell with two bunks and a toilet with no seat behind a plastic shower curtain, just three feet from the face of the unfortunate on the lower bunk. And had to try to sleep on pillows harder than breeze blocks.

At least here, in Ford, he knew each prisoner had his own decent, if cramped, cell.

After a couple of minutes, a second door opened and an officer, with keys hanging from his belt, greeted him with a friendly smile and an outstretched hand. ‘Detective Super-intendent Grace, don’t know if you remember me from Lewes prison, a couple of years ago?’

Roy Grace, who had a near-photographic memory for names and faces, looked at him. Short grey hair and rounded shoulders. ‘Andrew Kempson?’

‘Well, I am impressed!’

Roy shrugged.

‘Very good to see you again, sir. The Governor thought it best you came after general visiting hours were over, and he’s arranged for you to meet former Detective Sergeant Batchelor in a private interview room, cameras off, and the Governor knows you are going to be handed some evidence.’

Unlike some prison officers, Kempson at least seemed refreshingly respectful to his charges. Roy Grace followed him across a wide, open courtyard, past a row of prefab single-storey buildings. Several men were mooching around, some stooped, with that air of total defeat he’d observed on previous prison visits, others looking more determined and purposeful. One, with a rake and bin bag, looked like he was actually happy to be doing something useful.

They entered a large room that felt like an impoverished, denuded public library. Several prisoners were seated at bare tables, either reading newspapers or books, in front of racks of shelves containing, almost exclusively, crime novels. Among them he noticed several by Martina Cole, Kimberley Chambers and Ian Rankin. Following Kempson, Roy was ushered by the officer into a room at the far end.