The slice was given to Marion Polson, a former housekeeper at The Palace of Holyroodhouse in Edinburgh, by then-Princess Elizabeth following her nuptials in November 1947.

Polson worked for the Royals from 1931 to 1969 and was given the slice of cake as a thank-you for the “delightful” dessert service she had purchased for the couple.

Polson kept the slice, as well as its original presentation box and a letter from the Princess.

"My husband and I are deeply touched to know that you shared in giving us such a delightful wedding present,” the letter read.

"We are both enchanted with the dessert service; the different flowers and the beautiful colouring will, I know, be greatly admired by all who see it."

The slice was found in a suitcase that was placed under a bed following Polson’s death in the 1980s.

"It's a real little find, a little time capsule of glorious cake," said James Grinter of Colchester-based auction house Reeman Dansie.

"This one actually has its original contents, which is very, very rare.

"I don't think I'd particularly want to eat it, I must admit."

The cake was bought by a Chinese bidder who attended the auction via phone.