A Glasgow gangster, who was once called Scotland's most dangerous man, has spoken for the first time in almost a decade on his time inside controversial Special Unit. In a new book about the unit, and a documentary, he tells how the pioneering concept created by prison officer Ken Murray transformed him from feared caged killer to sculptor and best-selling author. Boyle, then 23, had been sentenced to life in 1967 for the murder of William "Babs" Rooney, reports the .

He started rioting and attacking prison officers behind bars. He was subjected to prolonged solitary confinement in cells including the notorious cages in Porterfield Prison in Inverness. But in 1973, he was one of the first to be transferred to the newly-formed Barlinnie Special Unit (BSU) where prisoners were encouraged to develop artistic talents as part of their rehabilitation.

Boyle, 80, said: "It's hard to describe how difficult it was for each of us to accept the Special Unit. The cell doors were unlocked at 6am till 9pm. "This degree of freedom was something we weren't used to.

"I can only guess that the intention was to encourage staff and prisoners to get to know each other and in a strange way this did work. "Ken explained how our past violence against prison staff meant officers resigned, creating a recruitment problem. "They wanted to bring the violence to an end.

" Inmates' cells were left unlocked, they could wear their own clothes and were on first name terms with officers. Boyle tells how he had .