One of Scotland's leading gangland figures Tam "The Licensee" McGraw has died, BBC Scotland has learned.
Tam "The Licensee" McGraw was linked to a range of serious crimes
For more than 30 years McGraw, who was in his 50s, had been linked to crimes ranging from drug smuggling to murder.
Paramedics were called to his home in Mount Vernon in Glasgow at about 1500 BST on Monday, where he was understood to have had a heart attack.
They tried to resuscitate him and he was taken to Glasgow Royal Infirmary but was found to be dead on arrival.
McGraw was found not proven of drug smuggling in 1998 and not proven of the attempted murder of a policeman 20 years earlier.
He had business interests in taxis and property and in 2002 suffered multiple stab wounds after being attacked at his home.
BBC Scotland's investigations correspondent Mark Daly said: "He was one of the most notorious gangsters that Glasgow has ever seen, spanning a career of up to 40 years which began in the 60s robbing local post offices.
"He's thought to have amassed a fortune of up to £20m and his speciality was drug dealing."
McGraw also had an involvement in the pub trade which is where he was thought to have gained his "Licensee" nickname.
However, rival gangsters thought the name came from his relationship with the police.
"They said it was because he was a police informant and that he was licensed to do pretty much anything he wanted," our correspondent said.
"It is also claimed it was McGraw's police contacts that allowed him to operate his heroin empire with such impunity.
"He also managed to escape lengthy prison terms and had a habit of 'getting off with it'."
McGraw was previously attacked at his Mount Vernon home
McGraw was also implicated in the notorious Ice-Cream Wars killings in 1984.
Thomas TC Campbell and Joe Steele spent 18 years in jail for the murders of six members of a Glasgow family but had their convictions quashed in March 2004.
Campbell later accused McGraw of being the man responsible.
Crime author Reg McKay spoke to BBC Scotland of his shock at McGraw's death.
"Even some of his enemies will take no joy in this," he said.
"A death is a death. The man had a wife and family.
"On the other hand there are some folk who feel very embittered by Tam McGraw and his behaviour over many years and who will indeed rejoice.
"He became one of the most powerful gangsters in Britain, certainly in Glasgow, and he earned a great deal of that power by trading information with the police."