Princess Diana's special surprise for Prince William on his seventh birthday revealed in newly-unearthed letter

A newly-unearthed letter Princess Diana wrote in 1989 shows just how special Prince William’s seventh birthday was.

• The letter has been made public as it is currently up for auction.
• In it, Princess Diana thanks the Metropolitan Police for organising a special motorcycle display for the little prince’s birthday.
• This follows royal news that the Duke and Duchess of Cambridge surprised NHS workers with sweet telephone calls.

Prince William and Prince Harry have often spoken of just how special their mother made their childhood.

And based on this newly-unearthed letter, it’s clear Princess Diana spared no effort when it came to her boys.

Dated June 21, 1989, the letter was sent by Diana to Sergeant George Plumb of Scotland Yard’s elite Close Protection Group, to thank him for organising a special motorcycle display for William’s 7th birthday.

It was written on official Kensington Palace letter-headed paper, and it includes the signature of the princess, as well as the signatures of birthday boy 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. I cannot begin to tell you what pleasure the display gave to all those little people and their mothers!”, Diana wrote.

“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.”

Another letter written Diana’s Lady-in-Waiting, Ann Beckwith-Smith, is also up for auction.

Addressed to Sgt Plumb’s boss - Chief Superintendent Wigglesworth – she also thanked the team for their special surprise.

“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,” she 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 letters - which can be seen here - are being auctioned by William George & Co, after being acquired by a private London-based collector from Sgt Plumb three years ago.

Robin Gray, managing director of William George, says of the auction, “We are delighted to bring this rare item, signed not just by Diana, Princess of Wales, but also by her children, to market.

“Authentic, personal pieces such as this are much sought after and we have experienced a lot of interest in this sale already.”