A bulletproof Rolls-Royce used by Princess Diana on her first trip to the USA is expected to fetch more than £1.2 million at auction.
The Rolls-Royce Silver Shadow was bought new in 1979 by the British embassy.
But it didn’t come into service until 1982 after engineers spent three years and $200,000 armouring the luxury car to repel bullets, grenades and even small bombs.
The silver limousine was used by the UK embassy in Washington and was the car which transported Princess Diana and Prince Charles on their state trip in November 1985.
During the trip, the Royals were frequently seen in the Rolls-Royce as they visited US President Ronald Regan and his wife Nancy.
The Royal engagement also saw Princess Diana, then 24, dance with John Travolta at a gala at The White House.
During the trip there were a number of anti-British IRA supporters protesting against the couple – with security as important as ever.
But they were well protected by the Rolls-Royce which was fitted with a 600-pound windscreen and equally hefty rear window.
The side windows, which are also bulletproof, were sealed against possible toxic gas exposure, and the exterior trim was fitted with intercoms.
The car is going to be auctioned off on Ebay by the Volo Auto Museum near Chicago, USA on November 9 – exactly 27 years after Diana’s visit.
Brian Grams, Volo Auto Museum director, said: “We just thought it was an armour-plated Rolls Royce that had been embassy-owned.
“But after digging through the documents and doing some research, we figured out what the car really was.”
Documents show in excess of $200,000 was spent armouring the Rolls-Royce, known as a Silver Wraith II in the USA, with experts valuing it at $2 million (£1.25m).
Under the bonnet is a 6.8-litre V8 engine which power transferred through a smooth three-speed automatic gearbox.
The museum has added that a portion of the sale of the car will be donated to Children with Cancer, the British charity which was late Princess inaugurated in 1988.
Other cars featured in the auction include Jon Bon Jovi’s personal BMW and the last car ever owned by Groucho Marx.