You can now own a slice of Princess Diana's wedding cake

You can now buy your own little slice of royal history ... because a piece of Prince Charles and Princess Diana's wedding cake is going up for auction.

But owning this 40-year-old slice of royal history won't come cheap, with Dominic Winter Auctioneers expecting the cake to sell for £500!

According to Dominic Winter Auctioneers, the cake slice is a 28-ounce portion - that's around 800g – from just one of the cakes the Prince and Princess of Wales had made for their royal wedding in 1981.

This particular slice - which is a classic British fruitcake baked by David Avery, the then head baker of the Naval Armed Forces - features a marzipan base and a royal coat-of-arms in blue, gold and red made out of sugar.

The cake was originally gifted to Moyra Smith, a member of the Queen Mother's household at Clarence House, shortly after the nuptials.

However, rather than eating it, Smith held on to it, keeping it preserved in cling film in a floral cake tin.

She even added her own handmade label, which read: "Handle with Care - Prince Charles & Princess Diane's [sic] Wedding Cake."

Smith signed and dated the label with the date of the wedding - 29/7/81.

The slice is being sold with an order of service, ceremonial details, and a royal wedding breakfast program.

Auctioneer and senior valuer Chris Albury said: "It appears to be in exactly the same good condition, but we advise against eating it."