A letter written by a six-year-old King Charles to his 'ill Granny' and found in a loft more than 60 years later has sold for £7,000.

The handwritten letter, on Buckingham Palace notepaper and dated March 15, 1955, and reads: "Dear Granny, I am sorry that you are ill. I hope you will be better soon."

On the back of the letter, a six-year-old Prince Charles wrote: "Lots of love from Charles." He signed off with colourful doodles and 14 "x" kisses.

The letter was found during a Christmas clear-out by a couple who live near Stratford-upon-Avon, who had no idea the royal letter existed.

The touching note from the future king was in a folder along with other royal letters which had been lying in a cardboard box for more than 40 years.

The couple also stumbled across a rare copy of the Queen's Christmas speech from 1956 - the year before the annual message was broadcast on TV.

A printed booklet is entitled "The Words of Her Majesty The Queen, Christmas Day Nineteen Hundred and Fifty-Six" and is a copy of the broadcast the late monarch delivered from her study in Sandringham.

The collection of letters were expected to fetch between £2,000 and £3,000 when they were sold at Hansons Auctioneers in London on Tuesday (March 7).

But a bidding war sent the price soaring until they were finally sold for £7,000.

The letters sold for £7,000 (image via SWNS)

The seller, a 49-year-old farm manager, said: "We finally had the time to look through a big box file that my mother had given to us.

"It originally belonged to my late grandad Roland Stockdale.

"It contained lots of royal memorabilia, including a letter from Prince Charles to his grandmother.

"My wife said 'wow, look at that!' We were pretty gobsmacked but we weren't sure whether anyone would be interested in it.

"My grandad passed away in his 70s in 1983 and the folder was inherited by my dad, who subsequently passed it to my mum over 10 years ago.

"She never had chance to look through it and gave it to my wife and I.

"Finally, at Christmas we had a bit of time to look through my grandad's folder.

The south Warwickshire couple never knew the letters existed (image via SWNS)

"For the last 30 to 40 years' it's been gathering dust inside various lofts.

"The royal memorabilia was a surprise but there is a simple explanation.

"My grandad, originally a farm worker from Carlisle, moved to London to find work and got a job with the Metropolitan Police.

"He went on to work for the Queen's personal protection force during the 1950s.

"The file includes pictures of him in the Information Room in Scotland Yard in 1952.

"I was told he was originally involved in helping to protect the Queen Mother but he probably worked with several royals over time."