A notorious serial killer who committed the World's End murders has died in prison aged 73. He died overnight at HMP Glenochil in Alloa, Clackmannanshire, the Scottish Prison Service confirmed. Angus Sinclair was convicted of killing four girls in his life time and spent more than half of it behind bars. The killings included the murder of two teenage girls in 1977, which he was sentenced to 37 years in prison for in 2014. He was also found guilty for a string of sex attacks on young children and detectives suspect he could have been behind several unsolved murders from the 1970s. The World's End murder 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. The minimum of 37 years in jail he was ordered to spend for the crimes was the same number of years the families of victims Christine Eadie and Helen Scott waited for justice. However, he was already in jail having been locked up since 1982 for sexually assaulting girls between the ages of six and 14. While already in prison for the sex attacks, Sinclair was given a life sentence in 2001 for the murder of Glasgow teenager Mary Gallacher in 1978. He had earlier served six years behind bars for killing a seven-year-old girl in 1961. At age 16 he pleaded guilty to culpable homicide and admitted 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. 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. Their bodies were discovered the following day in East Lothian. 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.