"I think he'll forgive me," she said. "I told him I wouldn't go above pounds 2,500, but I wouldn't have been able to sleep for three nights if I hadn't got them."
In tense telephone bidding, Mrs Buckley, 54, outbid auction rivals yesterday to secure the letters from the then Princess Elizabeth, now the Queen, describing her romance with the naval lieutenant Philip Mountbatten. It is thought to be the first time that personal letters from a reigning monarch have been offered for sale.
They describe how the couple first met, their shared passion for dancing and the thrill of driving along in his MG sports car. "Philip enjoys driving and does it fast!" the young princess told Betty Shew, a court correspondent who had asked for details for a book she was writing on the royal wedding.
Mrs Buckley set her heart on acquiring the writings as soon as she read about them.
They will now become the star attraction of the museum Mrs Buckley set up in Battle, near Hastings, Sussex, when her hobby of collecting assorted memorabilia took over her life and became a business.
She and her husband, Brian, gave up their newsagent's shop 10 years ago and opened Yesterday's World, a museum of everyday life since Victorian times which now welcomes 120,000 visitors a year, attracted by exhibits which include a Victorian chemist's shop and a 1930s-style children's nursery.
"We have this one room of royalty, with a life-sized animated Queen Victoria and this will go very nicely into it," Mrs Buckley said. "They're up there, we're down here, but it brings us all together."
The letters were put up for sale when they were discovered by lawyers among the papers of a relative of Mrs Shew's, a Miss Edbrooke. There were no other family members left to inherit them when Miss Edbrooke died recently in a nursing home in Somerset.
Marc Burridge, of Clevedon Salerooms in Avon, said he was delighted to be asked to sell them. The main London auction houses have agreed not to deal in private correspondence from the royal family dated after 1938 without permission from Buckingham Palace.
A Christie's spokeswoman said: "Letters between the Queen and Prince Philip we probably wouldn't sell."
But Mr Burridge said he did not consider the writings private as the details were published in Mrs Shew's book, also included in the lot.
"I thought about it very carefully but the information is in the public domain and it actually painted a very nice picture," he said after the sale.
Mrs Buckley, meanwhile, was pouring a glass of sherry for her husband. "I only started collecting things because he started playing golf," she said.
"He's got a lot to answer for, that boy."