SEX monster Angus Sinclair was let out of jail to sell toys to children.

Bosses at Peterhead jail let the psychopathic killer and paedophile come face to face with kids as he ran a toy stall in a sleepy fishing village.

Sinclair, widely regarded as one of the most dangerous murderers in Scotland, was unsupervised for much of his weekend release.

One of his victims was an eight-year-old girl.

Sinclair's shocking jaunt in Portsoy, Banffshire, is revealed in a new BBC documentary which names him as the likely killer of EIGHT women.

Phillip English, the former social work boss at Peterhead prison, told the programme he was horrified when he learned Sinclair had been allowed to sell toys he made in prison at Portsoy's annual boat festival.

He said: "I learned about the fact that Mr Sinclair went to the festival some time after it had taken place.

"I was very concerned. I had a very full and frank discussion with the governor at the time and made my position very clear.

"From the social work perspective, we were very deeply concerned about this and made our feelings known to the prison service."

A prison spokesman said the rules on letting sex beasts out on temporary release had been toughened up since Sinclair's chilling excursion in 1994.

He insisted: "The regime now in place applies an extremely rigorous risk assessment for any temporary release from custody."

Sinclair, 64, is still in Peterhead, serving life for two killings and multiple rapes.

The beast, who enjoyed strangling cats, raped and strangled Catherine Reehill, eight, in Glasgow when he was only 16.

Then, after he was freed on parole, he raped and murdered Glasgow teenager Mary Gallacher in 1978.

The BBC documentary, Scotland's Secret Serial Killer, suggests that by the time he killed Mary, Sinclair had already committed six other murders in a six-month orgy of violence.

A former FBI criminal profiler, Mark Safarik, told the programme he was convinced Sinclair killed World's End victims Helen Scottand Christine Eadie, both 17, in 1977.

And Safarik also blames Sinclair for the sex murders of Frances Barker, 39, Anna Kenny, 20, Hilda McAuley, 36, and Agnes Cooney in the same year.

He said: "I felt very strongly that these crimes had all been committed by the same offender. We had multiple, multiple areas of linkage."

Sinclair was only convicted of murdering Mary Gallacher in 2001after advances in DNA technology.

Then, in 2007, he was tried for the murders of Helen Scott and Christine Eadie, who were found dead after leaving Edinburgh's World's End pub.

Prosecutors said DNA linked Sinclair to the killings, but the case dramatically collapsed after the Crown failed to tell the jury about a vital piece of scientific evidence.

Thomas Young, now 75, was convicted of murdering Frances Barker and is still being held in Peterhead. He is appealing his conviction and Safarik's findings are part of his case.

Scotland's Secret Serial Killer will be shown on BBC 2 Scotland at 9pm tomorrow.