“It's no surprise that the 500K appealed to Hans Prym, who was a highly successful industrialist,” said Philip Kantor, Bonhams European head of motoring. “The vehicle was vast, stately, and incredibly powerful, only to be possessed by the elite.”

The car disappeared without trace for the next quarter of a century and later turned up in America. It was sold in 2011 for £2.9 million to Dutch car enthusiast Frans van Haren.

In another twist, it was seized by the authorities when Mr van Haren took it to a German car show, with the grandchildren of Mr Prym alleging it was stolen and the family were still the rightful owners.

In 2012, a court in Hamburg ruled that the US troops had no right to take the classic car and ordered that it should be returned to the family of its original owner.