‘Mad’ Frankie Fraser, 90, is on life support in a critical condition after being induced into a coma at Kings Hospital, in south London.

Fraser is one of the few surviving gangsters to live to tell the tale of the bitter struggle for supremacy between the Kray twins and the Richardson gang – his own employers – in the London underworld of the 1960s.

Fraser committed his first crime at 13 when he stole a packet of cigarettes and was sent to an approved school. During the Second World War he was christened ‘Mad’ Frankie after he feigned illness to avoid being called up.

In the 1950s he was bodyguard to gangland leader Billy Hill, taking part in bank robberies and carrying out razor blade attacks for £50 a time.

He later became ‘enforcer’ on behalf of the notorious Richardson gang, formed by brothers Eddie and Charlie. Fraser was charged in 1966 with the murder of Richard Hart – an associate of the Krays who was shot at a club in Catford. However, the charges were dropped when a witness changed his testimony.

The following year he was involved in a torture trial at the Old Bailey, during which gang members were charged with electrocuting, whipping and burning those disloyal to them. Fraser was accused of pulling out people’s teeth with pliers in a torture chamber, and was sentenced 10 years in jail.

Fraser’s last jail term ended in 1989, by which time he had spent 42 years of his life in prison for 26 offences. But the ageing villain achieved celebrity status in later life. He wrote his memoirs, appeared on television – where he told horrendous tales with dead-pan indifference – and even provided live commentary on coach tours of London’s gangland. The tour included the opportunity to share drinks, sandwiches and a chin-wag with ‘Mad’ Frankie at the infamous Blind Beggar pub in Whitechapel, where Ronnie Kray shot George Cornell – a Richardsons associate – in 1966.

Only last year a frail Fraser was handed an ASBO after flying into a rage when he found an 87-year-old man with dementia sitting in his favourite chair at their care home.

Fraser was admitted to hospital for a hip operation, but hospital staff spotted a fractured leg which may have been a recurrence of an old injury suffered during the brutal riots at Parkhurst Prison, on the Isle of Wight, in 1969. His son, Francis, 58, is among family and friends keeping a bedside vigil at the hospital.

Fraser’s ex-partner, Marilyn Wiseby – daughter of Great Train Robber Tommy Wiseby – told The Sun: “It’s a terrible shock. Frank is the most honest man I have known.”