LONDON, Aug 24 (Reuters) - A unique black Ford Escort driven by the late Princess Diana in the 1980s is due to be auctioned this weekend at Britain's Silverstone racing circuit.

One of 130 lots going up for sale on Saturday, the RS Turbo Series 1 mersin escort belonged to Diana between 1985 and 1988.
It is thought to be the only example of the model made in black, according to Silverstone Auctions, which expect it to fetch more than 100,000 pounds ($118,000).

The RS Turbo Series 1 was usually made in white but the royal family police guard asked for Diana's to be painted black "for discretion", the auctioneers said.

For the princess to drive the vehicle, which has just under 25,000 miles (around 40,000 km) on the clock, was "a very brave choice," Arwel Richards, Classic Car Specialist at Silverstone Auctions, told Reuters.

"All the other members of the royal family would be driving around London in the back... of an official car... and she's driving in a car... that you would see on a housing estate not outside the palace."

Next week marks 25 years since Diana died, aged 36, when the limousine in which she was a passenger crashed in a Paris tunnel as it sped away from paparazzi giving chase on motorbikes.

Other lots at the auction, taking place in conjunction with the Classic - a three-day motor racing festival at the Northamptonshire circuit - include a Rolls-Royce convertible once owned by Bee Gee Maurice Gibb.

The singer, who died in 2003, bought the black 1973 Corniche in 1979.

Decked out with red leather interiors, the vehicle stayed in the family until 2012. It is listed with a guide price of 100,000 - 115,000 pounds.

Also going under the hammer are a 1973 Rover P5, used to drive former British Prime Minister Margaret Thatcher upon her 1979 election to meet with Queen Elizabeth, with a guide price of 35,000 pounds - 45,000 pounds.

A 1988 Volkswagen T25 Caravelle GL 112 minibus used to transport late British physicist Stephen Hawking is being offered without a reserve price.

($1 = 0.8459 pounds) (Reporting by Marie-Louise Gumuchian; editing by John Stonestreet)