Prince Charles and Princess Diana's wedding cake is up for auction

This year marks 40 years since Prince Charles married Diana Spencer at St Paul's Cathedral on July 29 1981. More than 750 million people globally tuned in to the historic wedding.

A piece of cake from the royal wedding will be up on the UK auction block next week.

Dominic Winter Auctioneers expects the slice from the 40-year-old cake to fetch an estimate price tag of £200 to £300 (about RM1,175 to RM1,763).

How big was this Wedding Cake of the Century?

The main cake is made of a 225-pound, five-tier fruit cake designed by Dave Avery, the Royal Naval School of Cookery’s head baker.

The layers of the five-foot tall (165cm) official cake took about 14 weeks to prepare also had an identical twin made as an extra back-up.

Avery, now 78, told Australia’s 9Honey that, in a letter of appreciation after the wedding, the Prince and Princess of Wales mentioned "how thrilled they were with the cake," and that they even kept the second tier to use at Prince William's christening on August 4th, 1982.

The big piece of cake icing and marzipan base is from one of the grand set up of 23 official cakes made and distributed among important people and places.

The "sugared onlay" of the Royal Coat-of-Arms slice features a royal coat of arms in blue, gold, and red icing with a silver horseshoe and decorative borders along the top and bottom.

A piece of royal cake

According to the UK auction house, the single piece possibly came from the side of a cake or the top of a single-tier cake and is believed to been gifted to Moyra Smith, a member of the Queen Mother’s household at Clarence House, shortly after the nuptials.

Smith saved it in a floral cake tin instead of eating it, and even added her own handmade label, “Handle with Care - Prince Charles & Princess Diane’s Wedding Cake” with her sign and date of the wedding.

Smith kept the icing wrap up in plastic for many years, until her family sold it to the auction house in 2008. Chris Albury, auctioneer and senior valuer said “it appears to be in exactly the same good condition as when originally sold, ″ which has been sitting in a plastic-wrapped cake tin for four decades “but we advise against eating it.”

The winning bidder will receive two printed programs for the St. Paul's Cathedral ceremony along with the slice, as well as a program for a Royal Wedding Breakfast at Buckingham Palace.

However, the royal letter and bottle of commemorative beer that came with the lot are not included. The sugary artifact is estimated to be worth as much as £300, or more than $400, at the live auction on August 11.