When eccentric doctor and compulsive hoarder Harold Carr died at the age of 89, his relatives faced a daunting task to sort through his possessions.
His home was packed with piles of medical machinery, 1,500 beer steins, thousands of receipts and even a World War Two spy drone.
But all the effort became worth it when they opened the door of his garage - and struck gold.
Inside they found a 1937 Bugatti Type 57S Atalante, one of only 17 ever made.
The historic automobile with only 26,284 miles on the clock still has 99 per cent of its original parts.
It will be sold in Paris next month and is strongly tipped to surpass the £4.7million world record for a car at auction.
Auctioneers have put a reserve price of £3million on a two-seater described as one of the 'ultimate road-going sports cars from the golden era of the 1930s'.
And despite the credit crunch it could fetch anything up to £6million.
Fifteen of the 17 Type 57S Atalantes still exist. This particular model was originally owned by Earl Howe, a leading figure in the early days of British motor sport.
It has a 3.3-litre, eightcylinder engine, four- speed manual gearbox, can reach 60mph in ten seconds and has a top speed of 130mph.
Dr Carr, an orthopaedic surgeon who served as an army doctor during World War Two and also became a keen flier, bought the vehicle in 1955 for £895 - the equivalent of £15,500 today.
He drove it for a few years before leaving it in the garage near his home at Gosforth, Newcastle upon Tyne. The last tax disc expired in December 1960.
He never married and eight relatives are to share the proceeds of his estate.
A nephew, who wishes to remain anonymous, said: 'We knew he had some cars, but we had no idea what they were.
'It was a bit of local folklore that he had a Bugatti, but no one knew for sure. It's worth so much because he hasn't used it for 50 years. It was one of the original supercars.
'When it was built it could reach 130mph at a time when other cars could only do 50mph. Of course we are delighted and we're going to make sure the money is shared out among the family. It's a wonderful thing to leave.'
He described his uncle as 'a very eccentric old gent', adding: 'I suppose you could call him a mad doctor. People who saw him in the street thought he was a tramp. He would wear two pairs of trousers at the same time.
'All the children would laugh at him in the street when he tinkered with his cars because he wore a piece of rubber tube round his head to stop the oil getting in his hair. But he was always such a generous man.'
In his later years Dr Carr suffered from a form of obsessive compulsive disorder and hoarded everything in the house he refused to leave.
Files were piled 6ft high at his detached home, including even receipts for pencils bought in the 1950s.
'Since he died, it has taken me 18 months to get where I am today,' said the nephew.
'There was an awful lot to sort out with his house.'
A classic Aston Martin was found in another garage and sold for 'tens of thousands', but an E-type Jaguar was in such a poor state that it had to be scrapped.
Over the years Dr Carr resisted many offers to buy the Bugatti.
When his property was cleared dozens of notes from would-be buyers were found inside.
'People must have known because he got letters from all over the country,' his nephew said.
'He got notes pushed through his door. People travelled from all over to try and convince him to sell the car.'
James Knight, international head of the Bonhams motoring department, said Dr Carr's Bugatti was 'one of the last great barn discoveries'.
He added: 'I have known of this Bugatti for a number of years and, like a select group of others, hadn't dared divulge its whereabouts to anyone. It offers a truly rewarding project to the new owner - who will join a select list of distinguished owners - to play such an integral part in bringing this wonderful motor car back to life.'
The current auction record of £4.7million was paid in 1987 in London for another Bugatti, a 1931 Royale.