One of Scotland's most feared gangland figures, Tam "The Licensee" McGraw, died of a heart attack yesterday.

McGraw, 54, who was linked to crimes ranging from drug smuggling to murder for more than 30 years and whose fortune was estimated at about £15m, collapsed at his home in Mount Vernon, Glasgow, just before 2pm.

Paramedics attended and tried to resuscitate him. He was taken to Glasgow Royal Infirmary where he was declared dead on arrival.

Legal sources warned McGraw's death could lead to a potential vacuum and a turf war breaking out across Glasgow. They also said the Crown Office could move to try to recover some of the millions he allegedly earned unlawfully.

Nicknamed the Licensee, possibly because of his pub concerns, McGraw, who was married and had a son, was acquitted of the attempted murder of a police officer in 1978. Drug smuggling charges were found not proven in 1998.

He was also held for several days on suspicion of being involved in the infamous Ice Cream Wars in Glasgow's East End in the 1980s, but was released without charge.

Despite being linked to a litany of crimes he had not been convicted of an offence for about 20 years, leading to claims that he was a police informer. Police always denied this.

Last night McGraw's biographer, David Leslie, who penned Crimelord - The Licensee, which was published two years ago, said: "I was shocked to learn of Tam's death."

Donald Findlay, QC, defended McGraw in 1998 when a jury found not proven a charge that he funded a major drug-running operation between Morocco and Scotland.

He said: "Mr McGraw was a client of mine. I am sorry to hear of his death as frankly I would be with any human being, especially one I have encountered."

A senior legal source said: "McGraw was a man who has been around a long time. In his own line of business he commanded considerable respect from some and considerable dislike from others. But we know that nature abhors a vacuum.

"Now he has gone there will be great uncertainty and there is a good chance of turf warfare breaking out across Glasgow."