The royal wedding cake will be made by a businesswoman who has gone from kitchen table baking to selling her creations to the country’s best-known stores.

Fiona Cairns has been commissioned by Prince William and Kate Middleton to create a multi-tiered traditional fruit cake lavishly decorated with a floral theme.

Ms Middleton has given the cake designer detailed plans for the project which will be the centrepiece of the Buckingham Palace wedding reception.

The cake will be decorated with Prince William’s and Ms Middleton’s new cipher – thought to feature the couple’s entwined initials – which will be officially released on their wedding day.

Another theme will be the four flowers of the home nations – English rose, Scottish thistle, Welsh daffodil and Irish shamrock.

Ms Cairns, 56, whose sweet treats are sold in Harrods, Selfridges and Waitrose, was contacted by Prince William’s office last month and asked if she would make the couple’s wedding cake, which she agreed to do.

She added: “I couldn’t believe it, I’m very excited, very daunted and very privileged – a mixture of emotions. It’s multi-tiered, doesn’t have colour – it’s cream and white (icing) – and it’s a traditional cake but also quite delicate and modern, all the tiers will have a different theme.”

Prince William and Ms Middleton are fans of her fruit cakes, while Paul McCartney orders one for Christmas every year and she has also baked creations for Pink Floyd and Simply Red in the past.

The commission has been a process of discovery for the 56-year-old who has also been asked by Ms Middleton to feature around 16 different blooms and foliage for their meaning – known as the “language of flowers”.

Prince William’s fiancée also wanted elements from the Joseph Lambeth technique of cake decoration, where intricate piping is used to make three dimensional scroll work, leaves, flowers and other adornments.

The cake designer, who lives in Leicestershire, said Ms Middleton made her feel relaxed when they met around six weeks ago at Clarence House to discuss ideas, adding: “She has guided us right from the beginning and has quite strong ideas.

“That makes it much easier than a bride who has absolutely no idea whatsoever, which has happened in the past.

“But she knew very much what she wanted and she brought us mood boards and told us what influences she would like us to use on the cake.”

She would not say how many tiers the cake will have and said special ingredients would be added to the mixture.

But she did reveal it would include a range of produce from dried fruits like raisins and sultanas to walnuts, cherries, grated oranges and lemon, French brandy and free range eggs and flour.

The cake-maker said: “These are many of the ingredients we will be using in the cake, I can’t tell you exactly the recipe, but the brandy is very important, we always soak our fruits overnight to plump up the fruits.

“This is exactly the same method you would use at home if you were making a fruit cake - we just use bigger batches.”

The businesswoman sent samples of different fruit cakes toPrince William and Ms Middleton who chose their favourite and she has now started baking to allow the sweet treats the necessary four weeks to mature.

It is thought that the finished product will be featured in the palace’s picture gallery that is hung with priceless old masters. And it will be joined by another sweet treat – a McVitie’s chocolate biscuit cake – specially made for Prince William who is a fan.

Ms Cairns has been on a “sharp learning curve” since Ms Middleton asked her to incorporate flowers according to their meaning, something that was popular with the Victorians, who used the blooms to send secret messages.

She said: “I’ve been learning from Catherine and I’ve started making some of the flowers.

“There is the bridal rose which symbolises happiness, the oak and acorn – which is an architectural detail around the room where the cake will be – symbolises strength and endurance.

“There is a lily of the valley which symbolises sweetness and humility and ivy leaves which symbolise marriage,” she added laughing “I can’t remember all the flowers but I’m learning and we’re enjoying making them.”

Also on her list of flowers, which are created using sugar paste, is the aptly named Sweet William – which means perfection and gallantry.

Ms Cairns added: “We are also loosely interpreting the Lambeth technique, which is about sugar flowers but is about lattice work and scrolling, so we’re including that on the decoration of the cake too. We are going to make some garlands using sugar flowers which are another architectural feature in the room.”

Ms Cairns started her business with her 58-year-old husband Kishore Patel 25 years ago after he spotted the potential of her cake-making skills. She began working on her kitchen table then relocated to a small industrial park in Leicestershire. But the commission from Prince William and Ms Middleton is likely to make her name widely known.

The businesswoman joked about the time she met Prince William’s father the Prince of Wales at Fortnum & Masons in London around 10 years ago. She said: “I remember giving him one of our fruit cakes and the question he asked me was do I make wedding cakes.”