The Queen found the balloon while walking her dogs at Windsor Castle
A five-year-old boy from Buckinghamshire received a personal message from the Queen after she found a balloon he had released.
Charlie Castle was one of about 50 schoolchildren who released balloons during an end-of-term farewell at his school near High Wycombe in July.
The Queen came across it about 14 miles away, in the grounds of Windsor Castle.
A letter from Buckingham Palace to Charlie said the Queen was "so happy it was your balloon she found".
A numbered ticket was attached to the balloon, naming Charlie's school.
Call from palace
The Queen's personal assistant, Angela Kelly, was entrusted with returning it to Charlie, along with a note.
Anne Harding, head of Little Marlow school, said: "There was a message left on the school answer phone from someone who said they were calling from Buckingham Palace.
"I thought it could be a wind-up but when I made contact, I was told that the Queen would like to send a letter."
Mrs Harding said the school kept quiet about what had happened until the letter arrived last month.
When the envelope was opened, the little boy also found his green balloon tucked inside.
The letter read: "Her Majesty the Queen has asked me to write to tell you that she found your balloon in her garden at Windsor Castle when she was walking her dogs.
"Her Majesty was delighted to see how far it had flown and was so happy it was your balloon she found."
'Happy and excited'
Mrs Harding added: "It was a very lovely letter, written to the little boy.
"For the Queen to send it back, with the balloon, was really special.
"When his mummy mentioned it to him, he was very excited."
Kylie Castle, Charlie's mother, said she was "gobsmacked".
"In the letter she (the Queen) said she was very surprised to see how far it had come and she also said she hoped he had a lovely birthday.
"It was a very personal letter and he was very surprised and happy and excited."
Fifteen balloons were returned to the school, the furthest from Bordeaux in south-west France.