Final secret of the last Great Train Robber: With the death of Robert Welch at ... trends now

So now there is no one left. No survivors of the daring and violent raid on a Glasgow to London mail train in which £2.6 million in unmarked bank notes was stolen in just 46 minutes.

With the death at 94 of Robert Welch, last remaining member of the Great Train Robbery gang, a final secret goes with him to the grave.

Whose hand was on the iron bar that coshed engine driver Jack Mills so viciously about the head that he never truly recovered — and was a contributing factor to his premature death seven years later?

All Mills could recall was that one of his attackers wore a boilersuit and a green balaclava. Buster Edwards, played by the rock star Phil Collins in a romanticised drama of the 1963 heist that turned a gang of criminals and thugs into household names, was said to have been that masked man.

But he was never held accountable and later claimed it wasn't him who struck the driver, but he knew who it was. Indeed, the coshing of Jack Mills became almost a footnote because the sheer scale of the robbery, £61 million in today's values, was the 'biggest ever' haul.

Not long after the film Buster came out in 1988, Edwards took his own life.

Bob Welch would certainly have known who struck those blows. He was recruited as one of the 'heavies', intended to intimidate train staff into complying with the thieves' demands.

During his trial he was dubbed the 'man of steel' because of his powerful, broad-shouldered build and cold blue eyes. Years later he beat up a Sunday newspaper reporter who had called at his home to investigate a story about a betting coup at a dog track.

Yet, before his arrest, police decided he didn't fit the profile of the hoodlums they were looking for. They considered him too intelligent, running a legitimate South London drinking club business.

Welch had been careful to ensure he couldn't be linked to the crime, volunteering to the police that he was not involved. But he was careless: a handprint on a beer can placed him at Leatherslade Farm, the Buckinghamshire bolthole where the gang hid and shared out the cash from the 120 mail sacks.

He was jailed for 30 years and was among the first sentenced for what the judge Mr Justice Edmund Davies described as a 'sordid crime of violence inspired by vast greed'. Welch never spoke but bowed his head when sentenced.

His death, apparently from natural causes, although he had been suffering from Alzheimer's, comes almost three months after the 60th anniversary of the robbery. It means that all 15 of those convicted of a crime that Mr Justice Davies said should be stripped of any 'romantic notions of dare-devilry', are now dead.

Despite the judge's pleadings, the saga of the robbery became elevated to the 'crime of the century' and many of its participants, such as Ronnie Biggs, Bruce Reyolds and Edwards, were exalted as swashbuckling, almost lovable rogues to be admired for their madcap adventure.

Bob Welch was not one of these figures. He was the other side of that villainous coin. He did not swagger with chutzpah and charm. No rock 'n' roll stars sought friendship with him. And no celebrities beat a path to his door as they did to Ronnie Biggs's seedy flat in the dangerous suburbs of Rio de Janeiro, where he sponged off visiting journalists and pretended to enjoy the highlife but was in fact a prisoner of his own 'freedom' in Brazil.