When Princess Eugenie weds Jack Brooksbank on Oct. 12, the focus likely will be on her gown, her royal cousins Charlotte and George, and how her mother, Sarah, gets along with the rest of the royal family. But one part of the wedding that stays mostly behind closed doors is the royally fabulous wedding cake.

London-based cake designer Sophie Cabot, 33, was chosen to make the cake for Eugenie, who is the younger daughter of Queen Elizabeth’s second son, Prince Andrew the Duke of York, and his former wife, flame-haired Sarah Ferguson.

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“With great excitement I am able to announce that I will be making the wedding cake for Princess Eugenie and Jack Brooksbank,” Cabot posted on Instagram. “It has been the biggest secret I’ve ever had to keep!! I’m thrilled and honoured to have been chosen to create something so special and unique for this wonderful couple.”

Cabot started baking the cake on Wednesday for the Friday wedding, People magazine reports.

It will feature five tiers, three of red velvet and two of chocolate sponge cake, and will be covered with buttercream, white icing, and autumn decorations.

Princess Eugenie and her fiance Jack Brooksbank are preparing for their October wedding, which is said to be much different from Harry and Meghan's ceremony. (Twitter/Royal Family)

“They were very excited about having red velvet, during the tastings, red velvet and chocolate came out top,” Cabot told reporters, according to People. “It’s a lovely thing to have at this time of year as well – it’s a nice, rich cake.”

She also revealed that the dessert will contain 400 eggs, at least 53 packages of unsalted butter, 33 pounds of organic self-rising flour and 44 pounds of sugar. After all, it has to feed around 850 guests at Windsor Castle after the ceremony.

Those guests who are lucky enough to get a take-home piece might do well to save it. Past royal wedding-cake slices have sold at auction for big bucks, despite being long past their freshness date. Recently, slices from the weddings of Prince Charles to Lady Diana Spencer and Prince William to Kate Middleton sold for $1,920 apiece.

But not even the queen can exist on cake alone. Check out what the royal family really eats.

This story was originally published by The Daily Meal.