All aspects of Prince Charles and Princess Diana's wedding were extravagant and carefully planned, including their cake. The future monarch couple had a total of 27 wedding cakes, while the official one was supplied by the Naval Armed Forces.

David Avery, head baker at the Royal Naval cooking school in Chatham Kent, spent over 14 weeks on the five-foot-tall layered fruitcake. An identical cake was also made just in case one was damaged. The 225-pound cake was decorated with the Prince of Wales' coat of arms and the Spencer family crest.

A slice of the cake from the 40-year-old wedding was carefully preserved and will soon be auctioned off. The 28-ounce piece of cake, which has been kept in plastic wrap inside a decorative tin for four decades, will go up for auction on August 11. The iced slice is 8 inches by 7 inches, and features a white marzipan base decorated with a sugar facsimile of the pristine royal coat of arms in blue, red, and gold.

The treat, which is a rare item for collectors, was originally a gift from the Queen Mother, the late grandmother of the groom, to a then Clarence House employee named Moyra Smith. She stored the slice in a floral cake tin with a label on top reading, "Handle with care — Prince Charles & Princess Diane's [sic] wedding cake," with the date "29/7/81."

Smith sold it to a collector in 2008, who is now putting it up for auction, where it is expected to garner £500. Apart from the cake slice, several items from the ceremony including an order of service and a royal wedding breakfast program will also be auctioned off.

Chris Albury of the UK's Dominic Winter Auctioneers told the Huffington Post that the slice "appears to be in exactly the same good condition as when originally sold," however, he advised "against eating it."

Apart from the famous wedding cake, Charles and Diana had 26 other cakes at their wedding on July 29, 1981. One of the other wedding cakes was created by Belgian pastry chef SG Sender, who was known as the "cakemaker to the kings." Another cake was created by Chef Nicholas Lodge, who had previously made the Queen Mother's 80th Birthday Cake and was also commissioned to create a Christening Cake for Prince Harry.

Princess Diana and Prince Charles wedding cake
A well-preserved slice of Princess Diana and Prince Charles wedding cake AFP/Getty