LONDON (AP) - A royal butler's collection of letters, cards and photographs, including a thank you note from Princess Diana and requests for gin cocktails from Queen Mother Elizabeth, will be put up for auction Saturday.

Billy Tallon joined the royal household when he was just 15 and, over the next 51 years, became a trusted and valued senior servant. When he died last year, he left the vast, carefully preserved collection.

It also includes presents from the royal family, such as a silver ashtray engraved with a Royal symbol.

"This is a lovely collection of quite amazing bits and pieces," said Janet Canon at auction house Reeman Dansie. "Lots of people are flying in from overseas, especially from America and Canada to take part in the auction."

Tallon's long-term partner Reginald Wilcox also worked as an under butler in the royal household and Tallon inherited his memorabilia when he died. Saturday's auction includes some of Wilcox's possessions.

Billy, known affectionately as "Backstairs Billy," devoted his whole life to the royal family. He was especially attached to the Queen Mother, for whom he was chief steward. She died in 2002 at the age of 101.

His estate includes a handwritten note the Duke of Kent sent him after she died, saying; "I know all too well how grievous must be her loss to you and what an enormous gap she will leave in your life."

Canon said the auction of 700 lots was valued at an estimated $495,000 but was likely to sell for a lot more.

"There are people who really, really love the royal family and would pay anything to get some of these pieces," Canon said. "There is also some genuinely valuable pieces of art in the collection, too."

Canon said Buckingham Palace had inspected all the items and approved the auction, but a Buckingham Palace spokesman, speaking on condition of anonymity in line with Palace policy, would not comment on the sale.