The late Alan Longmuir said the figure of Paton, who was convicted of gross indecency with teenage boys and drug dealing offences, had cast a “malevolent shadow” over the book.

Longmuir, who suggests Paton benefited from friendships with politicians, police officers and senior members of the justiciary, writes of his fears that more will emerge about Paton that will show “his depravity ran deeper than we currently know”.

Longmuir, 70, died in hospital in Stirlingshire in June after falling ill in Mexico while on holiday with his wife, Eileen.

Tam Paton, former manager of the Bay City Rollers pop group, outside his house near Ratho, Edinburgh.

Longmuir describes how Paton, who is described in the book as seeing himself as “the great puppet master” behind the Rollers, was a “powerful and vindictive man not to be taken lightly”.

He also suggests that his brother and former bandmate Derek, who was convicted of possessing child pornography in 2000, believed he was “the victim of a set-up vindictively orchestrated by Tam Paton” as he started to becoming “increasingly threatening” after a legal action to try to recover missing royalties.

The Bay City Rollers sold more than 120 million records in the 1970s, but the band members, who also included Les McKeown, Stuart Wood and Eric Faulkner, saw little of the money that was generated by “Rollermania,” the phenomenon which saw them top the charts in Britain and America.

Longmuir, who claims in the book that he was groped by Paton while the pair were driving, reveals his concerns about what was going on at his mansion at Little Kellerstain, near Edinburgh Airport, after visiting him to ask for help to relieve financial problems.

Longmuir, whose book is published by Luath Press on 26 November, said: “Tam Paton casts a malevolent shadow over this book. I wanted to keep him out of it, but it has proved impossible. I hope I have kept the bastard at bay, at least.

“I am sure that more will come out on Tam and that his depravity ran deeper than we currently know. When people ask for my opinion on him I say he was a good man, gone bad.

“As the years have gone by I have gradually begun to realise how bad he had gone. He was a powerful and vindictive man not to be taken lightly. He had friends in high and low places.

“The friends in high places included politicians and senior members of the police and judiciary. The friends in low places included scum that would slash your face for a bag of Tam’s finest Colombian cocaine. A dangerous combination.

Recalling his last face-to-face encounter with Paton, Longmuir said: “It was a ranch-like building that Tam had built to his own specifications in the 1970s – on the inside it was pine-panelled like a Swedish sauna. There was a row of identically kitted out bedrooms which aroused suspicion.

“He flopped in a chair, legs wide apart, wearing elasticated jogging bottoms and an old, stained shirt. Remote controls were stacked up beside him.

“He told me he had a control room where there were banks of CCTV screens giving him viewing access to every corner of the house. And there were a lot of corners. I didn’t know whether the surveillance was for security or voyeuristic reasons. Both, probably.

“I had come to see him to borrow money. Five hundred pounds, I think it was. I was temporarily embarrassed for ready cash and there was a pressing bill to pay.

“I figured that Tam would be sufficiently guilt-ridden knowing that I knew he knew we’d been royally turned over and because of that he’d lend it to me. Before I got to the point I could not help noticing boys drifting around the house. They could have been 14. They could have been 18. , I don’t reckon shaving foam was a major item on the Little Kellerstain shopping list.

“‘Who are all these boys, Tam?’ I asked.

“‘They’re Edinburgh’s waifs and strays’.”

My brow furrowed.

“‘Alan, the police bring them here. It’s all above board. The police find them on the streets and to keep them out of trouble they bring them here. They know I will give them food and shelter. They know I will put them on the straight and narrow. If they go into care they run away. If they come here, they stay. They get jobs. They go straight’.”

Born in Edinburgh on June 20, 1948, Longmuir was brought up in a Gorgie tenement flat in Caledonian Road.

Alan discovered rock ’n’ roll at ten years old when he saw Jailhouse Rock at the Scotia Picture House on Dalry Road. Seeing Elvis Presley set him on the path that would see him become one of the biggest pop stars of his generation.

In 1965, at the age of 17, together with brother Derek, cousin Neil Porteous, Nobby Clarke, a classmate of Derek’s at Tynecastle High, and Dave Pettigrew, bassist Alan formed the band that would become the Bay City Rollers.

Initially known as The Saxons, they would undergo a number of name changes before settling on the moniker that would see them become an international phenomenon. From 1971 to 1976, the Rollers scored ten hits in the UK including two No.1s, Bye Bye Baby and Give A Little Love, and one US No1 with Saturday Night.

They also had TV series both in the UK and in America, leading Longmuir to Hollywood where he rubbed shoulders with stars like Britt Ekland and David Bowie.

The hysteria which erupted when he decided to leave the band in 1976 caused questions to be asked in the House of Commons about how one pop star could have so much influence over the youth of the day, and he returned to the band two years later.

In 1999, the Bay City Rollers were brought together for a one-off concert. Longmuir, Wood and McKeown embarked on a series of reunion shows in 2015.

Late Bay City Roller Alan Longmuir: Tam Paton depravity '˜ran deeper than we know'