The Ford Escort Prince Charles bought Princess Diana as an engagement gift is set to go under the hammer

The car is expected to fetch an estimated £40,000 when its sold by Essex-based auction house Reeman Dansie on June 29.

The owner, a Diana super-fan, told The Sun: "Of course I knew when I bought it that it once belonged to Princess Diana, that is why I wanted it. I was a big fan of hers.

"I have driven it around as a second car ever since. A lot of people ask me why I had it and I used to tell them that it was my first car I passed my test in and that I was attached to it.

"I felt that its history and provenance were so unique and I didn't want many people knowing.

"I have maintained it and had it regularly serviced and kept it in my garage. It is an excellent little runner and has always been reliable.

"I have had it for 20 years and now feel the time is right to sell it on."

Lewis Rabett, of Reeman Dansie, said: "Obviously it is a humble Ford Escort but who its first owner was takes this car to a whole other level.

"The vendor has been very coy about the true history of the car.

"She didn't let on that it used to be Princess Diana's car. I think she quite liked the fact that she was the only one who knew about it.

"The car has spent most of its life in a garage and is in very good condition for a car of that age and is in full working order.

"Diana didn't have it for very long and when she got rid of it she kept the frog mascot. The one on the bonnet of the car now is a copy."

The late royal - who passed away in a car crash in 1997 - drove the car between May 1981 and August 1982.

And she is believed to have held onto a silver frog ornament that was on the bonnet - a gift from her sister Lady Sarah Spencer - which was replaced.

Prior to its current owner, the Escort was sold for £6,000 to an antiques dealer as a gift.