A car given to Diana, Princess of Wales as an engagement present is to be auctioned after the current owner kept its origins a secret for 20 years.

The Prince of Wales gifted her the 1981 Ford Escort Ghia Saloon in May 1981.

The car is estimated to fetch between £30,000 and £40,000 when it is listed at Reeman Dansie’s Royalty, Antiques and Fine Art Sale in Essex on 29 June.

It has its original registration, 83,000 miles on the clock and retains its original paintwork and upholstery.

The car also has a copy of a silver frog mascot given as a gift to the princess by her sister, Lady Sarah Spencer.