Princess Diana sent a personal thanks the Metropolitan Police for helping entertain the princes during William's 7th birthday

By Phil Boucher
April 10, 2020 02:33 PM
Tim Graham/Getty

Prince William and Prince Harry have often spoken about the special times they spent with their mother Princess Diana in Kensington Palace.

Now, thanks to a heartfelt letter being auctioned in the U.K., royal fans can enjoy a tiny glimpse of just how meaningful that time was.

The handwritten note, dated June 21, 1989, was sent by Diana to Sergeant George Plumb of Scotland Yard’s elite Close Protection Group to thank him for organizing a special motorcycle display for William’s 7th birthday.

Written on official Kensington Palace letter-headed paper, it includes the signature of Diana — who tragically died in August 1997 — and the youthful scrawled signatures of William and a then 5-year-old Harry.

“Dear Sgt Plumb, It was so very kind of you and your team to have come here today on William’s birthday,” Diana writes in the letter. “I cannot begin to tell you what pleasure the display gave to all those little people and their mothers!

“I know how particularly busy you all are at the moment, so it meant even more to us that you and the motorbike boys were able to take part in the birthday celebrations! This comes with our warmest possible thanks.

“Yours sincerely Diana, William, Harry.”

Princess Diana’s letter
The William George Auction House
Princess Diana’s letter
The William George Auction House

A second letter sent from St.James’s Palace by Diana’s Lady-in-Waiting, Ann Beckwith-Smith, to Sgt Plumb’s boss – Chief Superintendent Wigglesworth — reinforces the royal family’s thanks.

“The Princess of Wales was enormously grateful to Sgt. Plumb and his team for ensuring that Prince William’s seventh birthday was such a very special occasion and the display was enjoyed by grown-ups and children alike,” Beckwith-Smith wrote.

“Her Royal Highness was particularly grateful to the ‘team’ for being able to fit this is on a day already full of official engagements, which was not helped by the rail, underground and bus strike. It was greatly appreciated and I would be grateful if special thanks could be passed to all concerned, but especially Sgt. Plumb.”

The William George Auction House

The letters are currently being auctioned online by William George & Co alongside a registered Buckingham Palace envelope addressed to “Sgt George Plumb Special Escort Group” in Diana’s handwriting.

Princess Diana’s letter
The William George Auction House

Can’t get enough of PEOPLE‘s Royals coverage? Sign up for our free Royals newsletter to get the latest updates on Kate Middleton, Meghan Markle and more!

Concluding on April 23, the highest bid for the items — which were acquired by a private London-based collector from Sgt Plumb three years ago — now stands at just over $9,000. The minimum next bid is $10,000.

Princess Diana, Prince William and Prince Harry
A.G. Carrick/Diana Memorial Fund/Getty
Princess Diana’s letter
The William George Auction House

“We are delighted to bring this rare item, signed not just by Diana, Princess of Wales, but also by her children, to market,” says Robin Gray, managing director of William George. “Authentic, personal pieces such as this are much sought after and we have experienced a lot of interest in this sale already.”