The main cake, which will take centre stage at the Buckingham Palace reception on April 29, will be made by celebrity cake maker Fiona Cairns who counts former Beatle Paul McCartney and rockers Pink Floyd among her clients. http://www.fionacairns.com/
Cairns said Kate had played a key role in designing the cake.
"She has guided us right from the beginning and has quite strong ideas," said Cairns, who started her business at her kitchen table a quarter of a century ago in Leicestershire, central England.
The cake will be decorated using cream and white icing with a "strong British floral theme" employing the Joseph Lambeth technique, a traditional English style that uses three-dimensional scroll work.
It will contain dried fruits such as raisins and sultanas to walnuts, cherries, grated oranges and lemon, French brandy and free range eggs and flour.
Each tier will be made unique by delicate, handmade decorations that have been personally requested by Kate. The ornate features of Buckingham Palace will be reflected on the cake,but most of the decorations will be floral, and each has a meaning.
"I've been very much learning from her. But she has selected these flowers," said Cairns. "For example, the bridal rose symbolizes happiness, the oak and the acorn symbolize endurance ... and we have a long list. We haven't made Sweet William yet but we will."
The decorations will also feature William and Kate's new cipher, thought to feature the couple's entwined initials, which will be officially released on their wedding day.
But the second, less formal cake will have a special resonance for William. The prince asked British biscuit maker McVitie's to create it according to a special recipe from the kitchens at Buckingham Palace. http://www.mcvities.co.uk/
"It has a couple of secret ingredients we can't tell you about but it will have dark chocolate, to give it a really nice flavour, and use rich tea biscuits that will be broken up."
McVitie's have made wedding cakes for the royals for decades, including for the diamond wedding anniversary of Queen Elizabeth II and Prince Philip in 2007.