The Queen set to watch Andy Murray

Andy Murray went into his epic battle with Andy Roddick for a place in the men's final with the prospect of the Queen watching on Sunday.

Sources said the Queen was expected to respond positively to the invitation extended to her to take a seat in the royal box for the first time since 1977, when Virginia Wade was the last Briton to win a singles title.

"Her Majesty is invited each year, but if there is a British representative in Sunday's final it is increasingly likely that she will accept the invitation," said one official.

"It will be a fantastic occasion to have a Briton vying for the championship for the first time since 1938 and the Queen on Centre Court to witness it."

Bunny Austin was the last Briton to appear in a men's final. Two years before that Fred Perry was triumphant, the last time a British man picked up the trophy.

Murray, 22, the No 3 seed, was taking on No 6 seed Roddick in front of another Andy, as the Duke of York had asked for a seat in the Royal Box this afternoon. His guest was Swedish businessman Johan Eliasch, who has an estimated fortune of £360 million.

Mr Eliasch, 45, is chairman and chief executive officer of Head, the sports goods manufacturer.

Also among the guests were Princess Alexandra, Princess Michael of Kent, Viscount Linley and the Duchess of Gloucester.

Former court stars Bjorn Borg, Rod Laver and Ilie Nastase were watching, and television journalists Sir Michael Parkinson and Sir David Frost were among the invited guests. Dame Maggie Smith was there, too.

David Beckham sent Murray a "Good Luck" message on his Twitter site.

But tennis fans who had queued in soaring temperatures throughout the first 10 days of the tournament, hit out at the lack of tickets available for this afternoon's semi-finals.

Eleanor Parfitt, 29, of Battersea, said: "It has been tough queuing for tickets each night in the park and even tougher to not be given that right today.

"I am still going to be on Murray Mound in front of the big screen, but I worry that the real fans are going to be there and Andy won't be able to hear us. Wimbledon need to sort this problem out for next year because tennis needs fans like me who shout till they can shout no more."

Sally Wilson, 21, of Brighton, said: "We'll still make a lot of noise on Murray Mound and it will still be a fantastic experience."

Max Butler, 34, of Harrow, said: "I put my name into a draw for the right to buy tickets about three months ago and I got two for today. I work in an office and one colleague offered me £1,000 for my tickets, but money isn't that important. This is going to be a great day for me and my girlfriend."

Wimbledon released around 600 tickets through an agency last night and within minutes they had been snapped up by canny online fans.