By Pallab Ghosh
Science correspondent, BBC News
How did Caine's character get out of his fix?
The Royal Society of Chemistry has announced the winner of a competition to solve the conundrum at the end of the iconic UK film The Italian Job.
In the film, the robbers' coach almost drives off a cliff, ending up balanced precariously on the edge, with the gang at one end and their gold at the other.
The RSC asked for ideas to get the gold off the coach before it tips over.
John Godwin from Surrey came up with the winning idea which involves draining fuel from the vehicle.
In the conclusion to the 1969 movie, Charlie Croker, played by Michael Caine, tries to reach the gold, but as he does so, the coach tips up dangerously.
Then gang leader Croker turns around and says: "Hang on a minute lads, I've got a great idea."
So what was the idea?
Some 2,000 members of the public put forward their own theories. Many of them were from children.
Twelve-year-old Thomas Nixon's homonym solution was for the gang to sing until they all got "frogs" in their throats. The frogs start to jump up and down which rocks the bus. They use the "rocks" to weigh down the end of the bus.
Eventually, the gang's throats become sore from the singing. And with the "saw" they cut the gold bullion in half. Because two halves make a whole - the gang could sneak the gold through the "hole".
But the winner, John Godwin from Godalming, had a more practical solution involving a three-stage process.
First, the coach needed to be stabilised. This involved smashing out the windows on the part of the coach overlooking the drop and smashing them inward at the front end to improve the weight ratio slightly.
One of the bullion raiders is then lowered outside and deflates the wheels to stop the coach from rocking.
Second, its weight distribution needs to be changed, particularly over the rear of the coach which is overlooking the drop. This involves emptying the fuel tank which John Godwin discovered was at the rear of the coach. This, he estimated, would contain 140kg of fuel.
Third, he would allow a member of the team to leave the coach and bring rocks in to the front of the vehicle to ensure it was stable and the gold could be removed.
"There're several sheets of maths here," said John Godwin.
"It was a good long day with a calculator. It's more than 20 years since I saw the film - I remember thinking there must be some way of getting that gold off the bus.
"I always had an idea of how they might solve this - so when the Royal Society of Chemistry put this out to the public as a competition it seemed like the ideal opportunity to see if it would really work or to see if it was hot air."