For now, though, as day turned to night, he was reading about Tony Barlow. Eight years back, Barlow had been the victim of a sustained and brutal beating on some parkland close to where he lived. He had been walking home from the pub when, as he had put it in his witness statement, ‘they came out of nowhere’. Four or five men, he believed, armed with pickaxe handles or metal bars.

‘Cops,’ he said. ‘I’d swear to it.’

Not that they’d been in uniform. Dark, unbranded hoodies, denims and trainers. But Tony Barlow had had enough dealings with the law to know police officers when he saw them, even if they were in mufti. He was a petty criminal with a lengthy string of convictions, and the immediate reaction of the investigating officers to his claims could best be described as healthy scepticism. Much more likely surely that this was the result of a falling out amongst thieves, Barlow too savvy to grass up his actual assailants while happy to point the police towards their own.

‘Said I was to stay away from kids,’ he told the investigators from his hospital bed. ‘Or else worse was coming. I told them I don’t have kids. “You know what we mean,” they said.’

A CID detective called Bobby Wilson had proposed a theory of mistaken identity. A paedophile ring had been operating in Edinburgh’s Old Town at the time. Police were on to them, but no arrests had yet been made, insufficient proof having been offered to the procurator fiscal. The notion that officers might have taken the law into their own hands was discussed, but nothing came of it.

But now Alan Fleck was hinting at Rebus’s involvement, and that interested Fox mightily.

Tony Barlow had spent weeks in hospital and many months afterwards undergoing physio to help him walk again without pain. Eventually he’d gone back to his regular source of income and been arrested and charged several more times. When pressed as to why he thought his attackers had been policemen, he’d said that they ‘spoke like the filth and smelled like the filth’.

Fox could understand why no great effort had gone into probing his accusation.

He’d found a phone number for Bobby Wilson – now himself retired – and had discussed the case with him. Wilson had no doubt that if it had indeed been a punishment beating, the most likely source was Tynecastle police station.

‘Alan Fleck wouldn’t have liked it,’ he’d told Fox, ‘if he thought a bunch of paedos were getting away with it.’