A 40-year-old slice of Charles and Diana’s wedding cake sells for $2,500 at auction

A 40-year-old slice of Prince Charles and Princess Diana's wedding cake has sold at auction for more than $2,500.

The "large slice" of icing and marzipan, which came from one of 23 official wedding cakes made for the royal wedding in 1981, sold Wednesday for £1,850 ($2,562) plus a 20% buyer's premium at Dominic Winter Auctioneers in Cirencester, England.

Prior to the sale, the lot was expected to sell for around £300 to £500.

Weighing around 800 grams (1.8 pounds), the icing features a sugared Royal Coat of Arms and a small silver horseshoe. It was given to Moyra Smith, an employee of the Queen Mother at Clarence House, whose family sold it to a collector in 2008.

"It appears to be in exactly the same good condition as when originally sold, but we advise against eating it," the auction house said on the lot's sale page.

The cake slice was bought by Gerry Layton, a private collector from the English city of Leeds.

Layton told The Yorkshire Evening Post he had "always been a monarchist" and would add the item to his estate, which would be left to charity.

"We were amazed at the numbers of people wanting to bid on this large and unique piece of royal cake icing," Dominic Winter auctioneer Chris Albury told CNBC via email.

He added that most inquiries had come from bidders in the U.K., the U.S. and the Middle East.

Prince Charles and Princess Diana were married at St Paul's Cathedral in London on July 29, 1981.

The icing layer was preserved in cling film inside an old cake tin, with a handmade paper label signed by the original owner taped to the lid. Its sale includes a printed Order of Service program for the wedding ceremony, as well as a memorial Royal Wedding Breakfast menu and table seating program for Buckingham Palace.