It was once dubbed the "crime of the century", and half a century on the Great Train Robbery remains one of the most audacious crimes in British history.
But the policeman who investigated it died thinking there were still some robbers who had got away.
Malcolm Fewtrell, the police officer who led Buckinghamshire CID at the time, died in November 2005 at the age of 96.
Before his death, he said he thought four robbers had got away with their part in the crime.
At the heart of the Great Train Robbery was notorious criminal Ronnie Biggs and mastermind Bruce Reynolds, who assembled a gang of at least 15 men for the job he called the "big one".
Reynolds' plan was to hold up the Glasgow to Euston night mail train - which was carrying huge numbers of used bank notes - as it passed through the Buckinghamshire countryside close to Cheddington.
As the gang waited, Reynolds, nicknamed "Napoleon", was so confident that he calmly lit a Montecristo No 2 cigar - but a series of blunders nearly spelled disaster and led to the ultimate capture of most of the gang, albeit some years after the crime.
The train appeared shortly after 3am and stopped at a set of fake signals the gang had put up and driver Jack Mills, who got out to see what was going on, was coshed over the head and knocked senseless.
But the gang found it impossible to unload the cash and the crooked train driver they had brought along with them, recruited by Biggs, couldn't work the controls.
Mr Fewtrell said: "These were dedicated professional criminals and it was all organised, but it could have failed at any time.
"They stopped the train at the false signals but they couldn't unload it because it was a sheer drop.
"They had brought along their own driver to take it where they needed to but when they sat him in the train he couldn't drive it."
"After hitting Mills so hard they then had to drag him back and make him drive it."
The train was driven a mile and a half to Bridego Bridge where the gang unloaded £2,631,684 in used notes - worth around £46 million today.
They then took the cash 25 miles by lorry to Leatherslade Farm, bought with the help of a crooked solicitor, where they planned to hole up until the heat died down.
But their warning to the handcuffed train staff not to do anything for 30 minutes as they made their getaway was the clue that helped detectives to conclude the gang was probably hiding within a radius of about 30 miles.
As the police closed in they divided the money and fled.
Mr Fewtrell said: "They weren't stupid but for professional, dedicated criminals they left an awful lot of fingerprints."
The gang had even played Monopoly with some of the loot and left fingerprints on the board.
A nationwide hunt was launched with the public urged to keep an eye out for people spending a lot of money and the names and pictures of some robbers were given to newspapers.
The first arrests - of Roger Cordrey and William Boal - were made in Bournemouth when Cordrey tried to rent a lock-up from a policeman's widow, and by December most of the robbers had been arrested.
Twelve were jailed for a total of more than 300 years but more than one broke out of prison, including Biggs, who spent more than 30 years on the run before he finally returned to Britain in 2001 to face arrest.
Reynolds returned in 1968, five years after the crime, and was captured in Torquay and jailed for 25 years.
The mastermind, who was released in 1978 then served another separate three-year sentence, died in February this year aged 81.
Before his death, he said: "As a career criminal you reach a pinnacle and that was it - it was a bit like a journalist finding out Hitler was still alive.
"Plus it had those elements of fantasy - I was brought up on Butch Cassidy and the Sundance Kid and Jesse James.
"Other crimes have got their points but for the audacity of it and the way it captured the public imagination, it's up there."
Biggs, who was released from prison in August 2009 on compassionate grounds due to ill health remains frail but - still defiant - managed to stick two fingers up to photographers at Reynolds' funeral earlier this year.
He is one of just a few members of the gang to live to see the 50th anniversary of their crime.
And Mr Fewtrell remained convinced before his death that some had walked free from the crime of the century, despite not revealing their names.
"We knew who they were but there was nothing on them. They didn't leave their fingerprints like some of the others," he said.
"They got away with their £150,000. They knew they were safe so they could still be in the country. I don't know where they went."