Serial killer and rapist Angus Sinclair, who was convicted of the notorious World’s End murders in Scotland, has died in prison aged 73.

The Scottish Prison Service confirmed he died overnight at HMP Glenochil in Alloa, Clackmannanshire.

Sinclair spent more than half his life behind bars for killing four girls as well as for a string of sex attacks on young children.

Angus Sinclair World End Murderer who has died.
The Scottish Prison Service confirmed he died overnight at HMP Glenochil in Alloa, Clackmannanshire (Picture: Alan Simpson)

But detectives suspect he could have been behind several unsolved murders from the 1970s.

His conviction in 2014 for raping and murdering two teenage girls in Edinburgh in 1977 resulted in him receiving the longest minimum sentence ever imposed by a Scottish court.

Sinclair was ordered to spend a minimum of 37 years in jail for the crimes – the same number of years the families of victims Christine Eadie and Helen Scott waited for justice.

But he was already in jail – having been locked up since 1982 for sexually assaulting girls between the ages of six and 14.

While still in prison for the sex attacks, Sinclair was given a life sentence in 2001 for the murder of Glasgow teenager Mary Gallacher in 1978.

However, he had earlier served six years behind bars for killing a seven-year-old girl in 1961.

Aged 16, he pleaded guilty to culpable homicide – admitting strangling Catherine Reehill in Glasgow and dumping her body on a tenement stairway.

It meant he spent around 40 years of his life locked up.

Undated picture of Helen Scott (left) and Christine Eadie, both aged 17, whose bodies were found six miles apart at Gosford Beach and Haddington, East Lothian, in October 1977, after they were beaten, raped and strangled following a night out in Edinburgh. Now detectives from Lothian and Borders Police hunting the killer of the girls have launched an interactive web page appealing for fresh clues to two of Scotland's most famous unsolved cases that became known as the World's End murders, after the name of a bar where the girls were last seen. 07/05/04: Helen Scott (left) and Christine Eadie, both 17, who were murdered in 1977 in Edinburgh and whose cases are part of seven unsolved murders of young women being linked by new scientific evidence, police said, Friday May 7, 2004. The girls were found dead several miles away from the World's End pub after being beaten, sexually assaulted and strangled. Three Scottish forces are investigating the links between a series of deaths in the 1970s and early 1980s, including the murders of Anna Kenny in August 1977 and Hilda McCauley in October 1977, both in Glasgow, Agnes Cooney in December 1977 in Lanarkshire, and Carole Lannan in March 1979 and Elizabeth McCabe in March 1980, both in Dundee.
Helen Scott (left) and Christine Eadie, both aged 17, whose bodies were found six miles apart at Gosford Beach and Haddington (Picture: PA)

It was following the Mary Gallacher case that police began to examine the link between Sinclair and several other unsolved murders.

The 17-year-old was raped and stabbed near a railway line as she went to meet a friend. Sinclair was linked to the crime years later following a DNA breakthrough.

Scientific advances later led detectives to Sinclair for the unsolved World’s End murders of 1977.

Christine Eadie and Helen Scott, both 17, were brutally killed after a night out at Edinburgh’s World’s End pub on October 15 1977, with their bodies discovered the following day in East Lothian.

They had been bound and strangled with their own underwear.

Sinclair was convicted of raping and murdering both girls with his brother-in-law Gordon Hamilton, who died in 1996, after a five week-trial in November 2014.

The prosecution was the first under changes to Scotland’s double jeopardy law which meant he could be retried for their murders after a court case against him collapsed seven years earlier.

The sentencing judge described Sinclair as a dangerous predator capable of sinking to the depths of depravity and said the words ‘evil’ and ‘monster’ were inadequate for him.

Editorial use only Mandatory Credit: Photo by ITV/REX/Shutterstock (9490082g) Ep2 Thursday 12th April 2018 on ITV Pictured Police picture of Serial killer Angus Sinclair In the second episode, Williams-Thomas investigates the notorious murders of Anna Kenny, Agnes Cooney and Hilda McAuley - who were all abducted and brutally killed in similar circumstances within four months of each other in Glasgow in 1977. 'The Investigator' TV Show, Episode 1 UK - 05 Apr 2018 The Investigator, is a three part ITV Documentray series in which award-winning former police detective, Mark Williams-Thomas, digs into several infamous missing women and unsolved murder cases, and uncovering new evidence.
His conviction in 2014 for raping and murdering two teenage girls in Edinburgh in 1977 resulted in him receiving the longest minimum sentence ever imposed by a Scottish court (Picture: PA)

The case, which became known as the World’s End murders, was for decades one of Scotland’s highest-profile unsolved crimes.

The then Lord Advocate Frank Mulholland, prosecutor in the trial, said the thousands of police officers who worked on the case through the years ‘never ceased in their endeavours to bring the girls’ murderers to justice’.

Sinclair had launched a bid to have the term for the World’s End crimes reduced but that was rejected by appeal court judges.

In a written judgment delivered in March 2016, they said of the 1977 murders: ‘Those appalling crimes demonstrated an immeasurable capacity for evil, depravity, and sadism.

‘The suffering of the victims and their bereaved families is, in our view, incalculable.’