The W-registration 1981 Ford Escort Ghia, with a distinctive silver frog fitted to the bonnet, was advertised for sale on the Internet by its antiques dealer owner, Keith Lawson.

He said that despite an offer of £2m and bids from the celebrities Mike Tyson and Stephen King he wanted the car to go to a museum.

The car's starting price in the Internet auction was $200,000

He eventually agreed to sell it through a classic car trader in California to an American museum.

The sale is expected to be completed shortly, but Mr. Lawson said he would not reveal the price and did not know the museum's name.

"We wanted the car to be seen by everyone. They offered a lower figure but we decided to accept it because they will put it on public display," Mr. Lawson said.

Calling it the "most sought after car of the decade" the Internet advert gave the highest offer received as $635,000.

'Good original condition'

The advertisement describes the car as in good original condition and available to be exhibited immediately.

It also mentions that gowns sold just prior to Diana's death were now being re-offered for more than $500,000.

Mr. Lawson from Norfolk said he bought the car for £6,000 in 1995 as a birthday present for his daughter. However, after Diana's death she had no longer wanted to drive it.

The car has travelled 80,000 miles and would only be worth about £600 without the royal connection.