Britain's Prince William is to marry his fiancee Kate Middleton on April 29, 2011 at London's Westminster Abbey, his office said on Tuesday.

William, son of heir-to-the-throne Prince Charles and the late Princess Diana, announced his engagement to long-term girlfriend Middleton last week after a courtship that lasted nearly a decade.

"We know that the world will be watching on April 29 and the couple are very, very keen indeed that the spectacle should be a classic example of what Britain does best," Jamie Lowther-Pinkerton, William's private secretary told reporters.   

He said Westminster Abbey had been chosen as the venue because of its long association with the royal family. Queen Elizabeth was married there and the funeral of William's mother Diana was also held there after her death in 1997.   

Retail researchers have estimated that the wedding could give a $1 billion boost to the British economy, but Lowther-Pinkerton said the couple were very mindful of the austere times facing many Britons following the coalition government's announcement of massive spending cuts.

"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."  A royal aide said that meant the royal family and the Middletons would pay for the ceremony, reception and the honeymoon, while other costs, such as the bill for security, would be met by the taxpayer.   

The royal aide said the couple, both 28, had always wanted a spring wedding and for it to be held on a Friday.   

Prime Minister David Cameron said it would be a public holiday. "The wedding of Kate and William will be a happy and momentous occasion," he said. "We want to mark the day as one of national celebration, a public holiday will ensure the most people possible will have a chance to celebrate on the day. - Reuters