Meghan Markle and Prince Harry’s “ethereal” tasting wedding cake will be displayed in a special installation, their baker has revealed.

Claire Ptak, who is making the culinary centrepiece for the couple’s big day, said the layered lemon and elderflower cake – in three parts of varying sizes – would be presented in a non-traditional way.

The final design will be unveiled on the big day although Meghan and Harry are in on the plans.

“You’ll have to wait and see on the day. It’s an installation of the way that we’re putting it out. It’s the last thing that we’ll reveal. It’s a non-traditional layout,” Ptak said. “It’s a slight shift from tradition.”

The chef, who owns the small, trendy Violet Bakery in east London, has been working with her team of six bakers full time for five days in the large kitchens of Buckingham Palace.

She described the flavour of the cake as being a balance of sweet and tart, combined with “ethereal” elderflower.

It is being decorated on the outside with a white, elderflower swiss meringue buttercream and is made of layered lemon sponge, drizzled with an elderflower syrup to a recipe specially created for the couple.

The layers are sandwiched with buttercream and lemon curd.

The ingredients for the royal wedding cake:

:: 200 Amalfi lemons

:: 10 bottles of Deborah Steward Sandringham Elderflower Cordial

:: 20kgs of butter

:: 20 kgs of flour

:: 20kgs of sugar

:: 500 organic eggs from Suffolk.

Some 200 Amalfi lemons are being used in the recipe, as well as 10 bottles of Sandringham Elderflower Cordial made using elderflower from the Queen’s Sandringham estate, 20kgs of butter, 20 kgs of flour, 20kgs of sugar and 500 organic eggs from Suffolk.

Ptak said: “It’s a lemon sponge – a special sponge that I developed just for the couple, and we drizzle the layers with elderflower cordial from the Sandringham estate so it’s really lovely and as local as you can get.

“We have a lemon curd made from Amalfi lemons which to me have the most delicious flavour. And then we’ve got elderflower swiss meringue buttercream.”

She added: “The buttercream is sweet and the lemon curd is very tart so you get a very lovely thing happening when you take a bite, which is to get all of these flavours and sensations perfectly balanced.”

Ptak, who is American like Ms Markle, said: “The elderflower is so quintessentially British to me as a Californian. It’s of this moment. It’s May so they’re just opening this week.

“It’s kind of an ethereal, floral flavour which I think is very special, especially for a wedding.”

Slices of the cake will be served to the 600 guests at the lunchtime reception in St George’s Hall after the ceremony.

Three types of Meghan’s favourite flowers peonies – Madame Claude, Bowl of Cream, and the aptly titled Duchess – in shades of white and cream will decorate the cakes, along with four different white and cream roses – Patience, Purity, Jeanne Moreau and Princess Miyuki.

The flowers will be removed before guests tuck in to the cake, but the slices will be served with edible rose petals.

The team from Violet Bakery, who were dressed in matching white polo necks, khaki trousers and cream aprons, have been working busily in the well quipped palace kitchen. 

Ptak, who was on Thursday removing one of the circular cakes from its large tin, before beginning to ice it with buttercream, was helped by Violet Bakery’s head baker Izaak Adams.

Discussing how the baking was going, she said: “There’s a few logistics of serving so many people at the same time. But it’s been a great process.”

She said Harry and Meghan “loved” the lemon and elderflower cake after trying a number of different samples. “They tried quite a collection,” she added. “What they said to me is that they really loved the idea of the seasonality and the freshness.”

The baker is not making a back-up cake in case of a disaster, saying: “It’s cake. It can’t go that wrong. We have enough cake and we don’t want to be wasteful. Anything that is left over, we were going to donate to charity.”

The chef had to call in some of her former workers to have enough staff to work on the cake and keep her bakery open.

Part of the cake is still being baked and iced.

It will be transported to Windsor Castle where the flowers will be added, and the installation assembled on the morning of the wedding.