Prince and Kate set wedding date

St James's Palace has also said the wedding - including the costs of the church service, music, flowers, decorations reception and honeymoon - will be paid for by the Royal family and the Middleton family.

The public will pay for associated costs like security. Downing Street announced that the wedding day would be a public holiday.

Jamie Lowther-Pinkerton, private secretary to Prince William, said the couple chose Westminster Abbey for its "staggering beauty", 1,000-year Royal history and intimacy despite its size.

By coincidence April 29 is the feast of St Catherine of Siena.

Mr Lowther-Pinkerton said those planning the nuptials were very conscious of Britain's precarious finances.

"All parties involved in the wedding, not least Prince William and Miss Middleton, want to ensure that a balance is struck between an enjoyable day and the current economic situation," he said.

"To that end the Royal family and the Middleton family will pay for the wedding."

He said this move drew directly from the precedent set by the Queen and the Duke of Edinburgh's wedding in 1947 and Charles and Diana's nuptials in 1981.

Mr Lowther-Pinkerton said William and Miss Middleton were "completely over the moon" about their engagement.

"I've never seen two happier people, which is absolutely fabulous to work in that sort of environment," he said.

"They're on Cloud Nine, like any other newly-engaged couple. They're now getting stuck into organising their wedding. They are very much in charge of the arrangements for the big day."

The couple announced their engagement last week, nine years after meeting as students at St Andrew's University, sparking fevered speculation about where and when they would tie the knot.