Letters from Queen Elizabeth II revealing her wonder at being a mother sold for double their estimates at auction on Saturday.

The two signed letters to her second cousin Lady Mary Cambridge, written following the births of Prince Charles in 1948 and Prince Andrew in 1960, show a tender side to the Queen.

The 1948 letter achieved £2,600 at the International Autograph Auctions event in London, £500 more than that detailing the newborn Prince Andrew.

"The baby is very sweet," the Queen writes following the birth of Charles. "Philip and I are enormously proud of him. I still find it hard to believe that I really have a baby of my own!"

Of Prince Andrew, she states: "Both the older children are completely riveted by him, and all in all, he's going to be terribly spoilt by all of us, I'm sure!"

The Queen’s letter following Prince Charles’ birth

Richard Davie, from the auction house, told the Daily Mail: "Rarely does the Queen convey such emotion to the population so it is fascinating to read about her feelings.

"The birth of Prince Charles was of course hugely important in the context of the future of the monarchy. But his arrival prompts the same maternal reaction in the Queen as with any other new mum."

Prince Charles: "Very sweet"

Investors may also be interested in a signed photo of the Queen with her husband and small children, as well as a signed Christmas card.