A 1937 Bugatti was kept in a Tyneside garage for half a century by its eccentric owner Dr Harold Carr.
When the reclusive genius died aged 89 last year, his nephews and nieces inherited what they thought was an ordinary suburban lock-up.
But inside they found a treasure trove of cars including a classic Aston Martin, a Jaguar E-type, and the rare Type 57S Atalante, now unveiled as the highlight of Bonham’s Retromobile car show and sale in Paris.
Left to gather dust for 48 years in a run-of-the-mill garage, since its last tax disc expired in December 1960, the black roadster could fetch as much as £6m for its new owners when it goes under the hammer.
If it raises only its reserve price tag of almost £3m, it will have increased 117-fold in value from the £895 Dr Carr paid Jack Barclays for it in 1955.
Other previous owners include Le Mans 24-hour race winner Earl Howe and Northumberland member of the gentry Lord Ridley.
The house of Bugatti is known for producing some of the fastest, most exclusive cars of all time. In his company's early years, Ettore Bugatti earned a reputation for advanced engineering and avant garde design, despite a lack of formal training. Only five cars were built in the company’s first year, but by 1911, Bugatti began its domination of the racetrack, winning the first ever Monaco Grand Prix.
Although forbidden to race by his father, the Atlantic's designer Jean Bugatti was killed while test-driving another Type 57.