Princess Diana had been often praised for her love for her children, Prince William and Prince Harry, and how she broke a lot of royal protocols in an effort to let them have normal lives. In an unearthed letter, which was auctioned by William George & Co, the notes showed how the People's Princess appreciated everything that was done for her kids by sending a thank you letter to the sergeant of Scotland for making the Duke of Cambridge's birthday more special.

The handwritten note was sent on June 21, 1989, to Sergeant George Plumb of Scotland Yard's elite Close Protection Group. According to People, the late Princess of Wales sent her heartfelt gratitude after the captain organized a special motorcycle display for her firstborn's 7th birthday.

Using Kensington Palace's official letter-headed paper, the note had Princess Diana's signature, along with the scribble of Prince Harry and Prince William's youthful autograph. "Dear Sgt Plumb, It was so very kind of you and your team to have come here today on William's birthday," she wrote. "I cannot begin to tell you what pleasure the display gave to all those little people and their mothers!

Prince Charles' former wife admitted that she knew how busy the protection group was at the time, so it meant a lot for the family that they went the extra mile to join the birthday celebration of Kate Middleton's husband. She ended her letter with her "warmest thanks."

Princess Diana's Lady-in-Waiting, Ann Beckwith-Smith, also sent a letter of thanks to Sgt Plumb's boss, Chief Superintendent Wigglesworth, from the St.James's Palace. She said the mother-of-two was "enormously grateful" for the deputy and his team's move for ensuring Prince William's birthday would be extra special, Yahoo UK noted.

They were also thankful that the managed to squeeze the event on their busy schedules amid the "rail, underground, and bus strike." They also assured that their effort was much appreciated, so they wanted to extend their thanks to all concerned, but most especially to Sgt. Plumb.

William George & Co is currently auctioning Princess Diana's letters, along with a registered Buckingham Palace enveloped addressed to "Sgt George Plumb Special Escort Group" in her writing. The sale will end on April 23, and the current highest bid is at 7,500GBP. The next bid is now at 8,000GBP as of this writing. 

William George managing director Robin Gray said they were all delighted to bring the rare item with Princess Diana, Prince William, and Prince Harry's signs to market. He said that this kind of authentic, personal pieces often caught a lot of interests and are a sought after by the auctioneers.