"Hang on a minute, lads. I've got a great idea," is still one of the greatest pay-off lines in British cinema. It was uttered by Michael Caine, playing the London villain Charlie Croker, immediately before the credits rolled on the 1969 heist classic, The Italian Job.
But for 40 years, no one has known what that "great idea" could possibly be, until yesterday, when Sir Michael revealed there was another ending.
The version shown in cinemas ends abruptly with Croker and his boys in a coach dangling over the edge of a cliff in the Alps. They have all crowded to one end of the coach, to prevent it from tumbling into the ravine. At the other end, is a mound of stolen Italian gold, sliding further and further out of reach.
So this year, to mark the film's 40th anniversary, the Royal Society of Chemistry (RSC) is holding a competition for the most convincing explanation of what happened next. It has already attracted 750 entries. The winner is to be announced in January.
Sir Michael, 75, speaking at the 2008 Visit London Awards, said the alternative ending would have set the scene for a sequel. It involved causing the stricken vehicle's centre of gravity to move forward fractionally by using up all the petrol in its tank, thus saving Charlie's gang, but not the gold.
"In the coach, I crawl up, switch on the engine and stay there for four hours until all the petrol runs out," Sir Michael said. "The van bounces back up so we can all get out, but then the gold goes over. There are a load of Corsican Mafia at the bottom watching the whole thing with binoculars. They grab the gold, and then the sequel is us chasing it."
Sir Michael was at the ceremony in the Albert Hall after being voted the capital's favourite Londoner, beating Joanna Lumley, Sir Alan Sugar, Paul Merton, Jamie Oliver and Leona Lewis.
The RSC is offering a three-night stay for two in Turin as first prize. Entrants have to give a "clear and creative" account of how Croker's mob might have got the gold without getting killed. Explanations can be no more than 150 words, the gang has only 30 minutes before the bus plunges over, and the solution must be based on "serious scientific task rigour".
One solution, offered by Dr Lewis Dartnell, an astrobiologist at University College, London, is that the gang should use superconducting magnets, but since gold is not naturally magnetic, it would have to be vapourised to a blindingly hot plasma first, and Croker would have to find solutions to extra problems as a cloud of superheated metal is sucked across the bus in the direction of the gang. "Hang on a minute," you can almost hear him say.Reuse content