felie din tortul de nuntă a Prințesei Diana cu CharlesThe generous portion is decorated with a royal coat of arms in red, blue and gold and was given to Moyra Smith, one of the Queen Mothers Clarence House employees, after the 1981 ceremony.
It has been preserved in cling film in a cake tin ever since and is expected to sell for £500 (GBP).
The cake tin has been kept with a note which reads: Handle with care. Prince Charles and Princess Dianes wedding cake, M.C Smith.
The 8in by 7in slice was kept by Mrs Smiths family until 2008, when it was acquired by a collector who is selling it with auctioneer Dominic Winter, in Cirencester, Gloucestershire.
The cake has lasted much longer than the ill-fated royal marriage, with Charles and Diana separating in 1992 and divorcing in 1996.
A total of 23 official cakes were made to celebrate the wedding, including a centerpiece five-tier fruitcake.
Mrs Smiths slice is believed to have come from a cake distributed to staff at the Queen Mothers official residence Clarence House to thank them for their efforts.
Dominic Winters royal memorabilia expert Chris Albury said: Its a curious and unique keepsake celebrating a royal wedding that holds an enduring fascination with British royalty aficionados worldwide.
I still wouldnt recommend eating it, but after 40 years its clearly destined to last.
The slice of cake will be sold on August 11 alongside an order of service for the St Pauls Cathedral wedding and Royal Wedding Breakfast program.
*BYLINE MUST CREDIT: Dominic Winter/Mega.
28 Jul 2021,Image: 623911846, License: Rights-managed, Restrictions: World Rights, Model Release: no, Credit line: Profimedia
