The Princess of Wales tried to marry off her sister to future husband the Prince of Wales, letters written by Diana reveal.

The teenage Princess played matchmaker between Charles and older sibling Sarah in the late 1970s.

But the royal, who went on to wed the Prince a few years later in 1981, admitted she was relieved the plan, run with the help of siblings Charles and Jane, had not succeeded.

The revelations are found in one of four unseen letters written by the Princess which are being auctioned later this month.

In one, Diana, who famously danced with John Travolta, described her love for the artform but said "watching me dance is like watching an elephant, so no-one does".

The notes were penned to Diana's nanny, Mary Clarke, who looked after the royal from the age of nine and her brother and sisters after their parents divorced.

In a letter written in December 1978 the Princess said: "For the last few years, Jane, Charles and I have been trying to marry off Sarah to various men but have failed in every direction.

"We even thought Prince Charles might have been in the running but were relieved when that passed."

The other letters mention Diana's excitement over her wedding, and her persistent morning sickness when pregnant with Prince William.

In one written in January 1982 the Princess mentions how she took Charles to her family home of Althorp in Northamptonshire but described how they had a few accidents.

"In our short stay we managed to break two Stuart chairs and a glass window," she writes.

Mrs Clarke was reported as saying: "It will be a wrench to let the letters go but I will always have my memories of Diana, who was such a wonderful woman."

The letters and other royal memorabilia are expected to fetch up to £8,000 when sold by auctioneers Reeman Dansie in Colchester, Essex, next week.

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