Elderflower cordial from the Queen's Norfolk estate and eggs from a farm in Essex have been used to make Prince Harry and Meghan Markle's wedding cake.
Chef Claire Ptak from Violet Bakery in London has been making the cake in the Buckingham Palace kitchen.
The lemon sponge was made from eggs laid at a farm near Ingatestone, Essex.
Ms Ptak will drizzle 10 bottles of the syrup made from the "ethereal" flowers grown at Sandringham over the cake's butttercream layers.
The cordial was made in the estate's visitor centre restaurant. The eggs were supplied by Longwood organic farm, which is based at Tuddenham St Mary near RAF Honington in Suffolk where Harry was stationed, and the farm sourced them from its Essex supplier.
Some 20kg (44lb) of butter, 20kg of flour, 20kg of sugar and 500 organic eggs were needed to make enough cake to feed 600 guests.
Its layers have been sandwiched with buttercream and lemon curd made from 200 Italian lemons from Amalfi and it will be covered with a white, elderflower Swiss meringue buttercream.
Ms Patak had her team of six bakers have been working on the cake for five days.
She described its flavour as a balance of sweet and tart, combined with "ethereal" elderflower.
Peonies - known to be Ms Markle's favourite flowers - in shades of white and cream will decorate the cake, along with four different white and cream roses.
The cake, which will be made in three parts of varying sizes, will be served at the lunchtime reception in St George's Hall, Windsor Castle after the ceremony.
However, its final design will not be unveiled until Saturday.
She said: "It's the last thing that we'll reveal. It's a non-traditional layout."
"It's a slight shift from tradition."