Angus Sinclair has died in prison at the age of 73 after spending decades in jail for a series of killings, rapes and indecent attacks on children.
The words "evil" and "monster" are inadequate ones to describe a "dangerous predator capable of sinking to the depths of depravity".
Those were the damning remarks of the judge who sentenced Angus Sinclair for the murders of teenagers Christine Eadie and Helen Scott.
It had taken the passing of 37 years and a change to Scotland's double jeopardy law before the killer was brought to justice for these two deaths.
But the Glasgow-born painter and decorator had killed before.
In 1961 at the age of 16, Sinclair was convicted of murdering his seven-year-old neighbour Catherine Reehill. He was sentenced to 10 years in prison and served six behind bars. In 1978 he killed 17-year-old Mary Gallacher in Glasgow, but was not convicted of that crime until 2001.
Detectives also suspected he had murdered four more women in Glasgow in 1977 - but did not have enough evidence to charge him.
Sinclair grew up in the St George's Cross area of Glasgow.
His obsession with sex was evident from an early age.
The teenage Sinclair had lured his first victim, Catherine Reehill, into a stairwell before raping and strangling her.
The calculated manner in which he disposed of the body and tried to cover his tracks shocked police.
He even called the ambulance himself, telling the operator that "a wee girl has fallen down the stairs".
The BBC uncovered a psychiatrist's report from the time which said: "I do not think that any form of psychotherapy is likely to benefit his condition and he will constitute a danger from now onwards.
"He is obsessed by sex, and given the minimum of opportunity, he will repeat these offences."
Killed and dumped
Despite the dire warning, Sinclair served just six years.
He was released in his early 20s, took up a trade, got married and had a son.
However, in 1977 there was a spate of murders across central Scotland.
Six young women disappeared after nights out, and were found dumped on deserted farmland or waste ground.
Two of those victims were teenagers Helen Scott and Christine Eadie, who had last been seen at the World's End pub on Edinburgh's Royal Mile.
The biggest manhunt in Scottish police history was launched. But it would lead nowhere.
At that time, police did not link the killings to another four murders which had happened in Glasgow within a few months of each other.
Frances Barker, 37, Hilda McAuley, 36, Agnes Cooney, 23 and Anna Kenny, 20, had been killed and dumped in strikingly similar circumstances.
All had been bound and gagged with items of their own clothing.
It would be a quarter of a century before police would realise the World's End and Glasgow murders were uniquely similar, and might be linked.
About a year after World's End, 17-year-old Mary Gallacher was abducted in Glasgow, before being raped and murdered.
Like the others, a ligature had been involved and she died from a knife wound to her throat.
But this time, Sinclair had been seen. There had been a witness to the abduction, and police had come close to identifying a suspect.
This close shave, criminologists believe, was the signal for Sinclair to change his tactics. He needed easier targets, and so he began to prey on children.
Between 1978 and 1982, Sinclair would rape or indecently assault countless children across Glasgow.
Angus Sinclair - a life of abuse, rape and murder
- 1959 - stole an offertory box from a Glasgow church, aged 13
- 1959 - housebreaking charge
- 1961 - committed lewd and libidinous practices on an eight-year-old girl. Sentenced to three years' probation
- 1961 - convicted of killing Catherine Reehill, aged seven. Sentenced to 10 years in prison. Serves six years
- 1970 - marries trainee nurse Sarah Hamilton (Gordon Hamilton's sister) and has a son two years later
- 1977 - thought to have murdered six women within seven months. Frances Barker, 37, Hilda McAuley, 36, Agnes Cooney, 23, and Anna Kenny, 20, all from Glasgow, as well as Christine Eadie and Helen Scott from Edinburgh
- 1978 - murdered 17-year-old Mary Gallacher in Glasgow
- 1980 - illegal possession of a .22 calibre revolver
- 1982 - pleaded guilty to rape and sexual assault of 11 children aged six to 14. Sentenced to life in prison
- 2000 - cold case review of 1978 Mary Gallacher murder
- 2001 - convicted of the murder of Mary Gallacher
- 2007 - trial for murders of Christine Eadie and Helen Scott collapses
- 2014 - retrial finds Sinclair guilty of World's End murders
He was finally caught in 1982, and pleaded guilty to 11 charges of rape and indecent assault, although he admitted his victims could have numbered in the hundreds.
He was sentenced to life in prison.
It would be almost 20 years later, when he was being prepared for parole, that one of his old crimes came back to haunt him: the 1978 murder of Mary Gallacher.
A cold case review revealed that Sinclair's DNA had been on the victim, and in 2001 he was found guilty of her murder.
Three years later, in 2004, cutting-edge science put Sinclair in the frame for the World's End murders.
His DNA, and that of his dead brother-in-law, Gordon Hamilton, was found on a semen stain taken from Helen Scott's coat.
Scottish police had planned to charge Sinclair with all six 1977 murders, but all the evidence from the unsolved Glasgow murders had been lost.
They also had the problem that someone was already in prison for the murder of Frances Barker - the first in the sequence from 1977 - and had been for almost 30 years.
Thomas Ross Young continued to plead his innocence until his death in July 2014.
Sinclair was prosecuted for the World's End murders in 2007 but the long-awaited trial ended in disaster.
The case collapsed when the judge said the Crown had insufficient evidence to proceed.
However, a change in the law on double jeopardy - the rule that meant a person could not be tried twice for the same crime - saw Sinclair become the first in Scotland to be given a second trial.
This time he was found guilty of the murders of the two teenagers and given a sentence that would have kept him in prison until he was 106.
No-one has ever been charged with the murders of Agnes Cooney, Hilda McAuley and Anna Kenny.