A remarkable collection of royal memos, cards and photographs is set to sell for £8,000 when it goes under the hammer at Hansons Auctioneers but could fetch far more. Part of the collection includes a hilarious note written by the late Queen explaining that her corgi puppies ate a royal photograph.

The memo was written to Alan Maxwell, the royals’ official photography expert who would develop their camera films and offer his advice. The handwritten note is among a treasure trove of photographs, letters and thank you notes the royals wrote to Mr Maxwell over his years of service.

The royal collection was discovered in a cardboard box 15 years after Mr Maxwell’s death and is now going under the hammer. The haul includes more than 60 Christmas cards and New Year cards sent out by the royals between the 1970s and 1990s.

Mr Maxwell was a photographic and camera specialist at London’s Wallace H Eaton Ltd, official suppliers to the royal family. The Royal Family relied on Mr Maxwell for all their photography needs, including helping them choose the annual royal Christmas cards.

Writing a memorandum note to Mr Maxwell before one Christmas the late Queen Elizabeth told him: “Please check the print with the negatives to find out which is missing - eaten by the puppies – ER.”

Another note written by King Charles when he was Prince of Wales in 1993, revealed how he felt about the “unpromising material” for that year’s cards. One of the sets featured him posing in a kilt next to Prince William and Harry while the others showed Diana posing with her sons. A third featured the Queen and Prince Philip.

In the note, he wrote: “Dear Mr Maxwell, I just wanted to thank you so much for all the time and effort you put into producing possible Christmas cards for me this year. I couldn't be more pleased with what you have achieved from some pretty unpromising material!

“I thought you did wonders in interpreting my ideas of having a card made up of three small pictures, and only narrowly preferred the group version in the end. I only hope it is appreciated by several thousand recipients.

"I am sorry that my ridiculously congested programme meant that you had a fruitless journey to London, and that I did not have an opportunity to congratulate you in person, but did want you to know how grateful I am for all you have done on this and other projects. What on Earth would I do without you?! Yours sincerely, Charles.”

Another letter being sold is one written by Diana in 1992 in which she thanked Mr Maxwell for “coming to our rescue”. She wrote: “Dear Mr Maxwell, A very special thank you for coming to our rescue at such short notice! I did appreciate enormously the speed in which the photographs arrived here & am only sorry for the trouble we must have caused! Yours most sincerely, Diana.”

Other Diana memorabilia includes multiple professional images of her taken in the 1980s and 90s including her 21st birthday portrait by Snowden. Another picture in the auction is a 1984 Christmas card, inscribed ‘Mr Maxwell, from, Diana and Charles’, features a photo of the couple with a small Prince William and baby Prince Harry.

A touching 1988 Christmas card, sent by Queen Elizabeth and The Duke of Edinburgh, features a photo of Elizabeth holding an infant Princess Beatrice of York on her lap with The Queen Mother standing by her side.

The most valuable lot, which is expected to fetch between £500 and £700, is a typed and signed letter from Queen Elizabeth to Mr Maxwell. Written on Buckingham Palace paper, the note thanks him for his good wishes on the Queen and Duke of Edinburgh’s golden wedding anniversary plus 13 photo memorandums to Mr Maxwell signed with the initials ‘ER’.

The note says: “Many thanks for getting a repeat for the picture of Harold Wilson and me - he's had them in his wallet for years! Practically rubbed it away. I am giving you a large and difficult order for copies of pictures I took of my Jersey cows that won prizes recently; with the help of a New Zealand farmer and his wife, and they want the photos for souvenirs! There is no immediate hurry as they've gone back to NZ. ER.”

Mr Maxwell died in 2009 and now his collection is being sold, with many of the notes and letters seen for the first time. Auctioneer Charles Hanson, owner of Hansons Auctioneers, said: “Members of the royal family always called him Mr Maxwell, not Alan.

“He was a man of absolute discretion, hence earning their respect. He printed Christmas cards and trimmed and framed them. He was an absolute perfectionist. Mr Maxwell, a Yorkshireman, passed away 15 years ago and now his collection has finally come to light.

“It’s important in terms of royal history but also allows us to pay tribute to a man held in high esteem by royalty. In the digital age it’s easy to forget that all photos used to be sent off to be developed and printed. The royal family, among the most photographed people in the world, came to rely on Mr Maxwell for their photographic needs and he was proud to serve them.”