BRITAIN'S Prince William will propose to his girlfriend Kate Middleton Friday, it has been claimed. Kate - who has been dating the 26-year-old royal for around six years - turns 27 today, and speculation William is planning to make her day extra special is rife. U.K. bookmaker Ladbrokes has halved the odds of the pair announcing their engagement to 5/1 after it was flooded with bets. Bookmaker William Hill has also decreased its odds of the prince popping the question during 2009 from 6/4 to 1/2. William Hill spokesman Rupert Adams said: "We have had hundreds of bets on Prince William and Kate Middleton getting engaged and almost all suggest that 2009 will be the year. Kate's birthday is the most popular possible date with bets of up to 100 placed, but should William hold back then Valentine's Day is a 14/1 shot." The sweethearts recently returned from a romantic holiday at the royal retreat of Birkhall, the Prince of Wales' home on Queen Elizabeth's Scottish estate Balmoral. William is said to have surprised Kate with a romantic evening in a secluded log cabin, further fueling rumors they are set to tie the knot. William Hill is offering a host of odds relating to the details of the expected royal wedding. After Prince William was recently spotted sporting bushy facial hair, the public are invited to take a bet on whether he will walk down the aisle with a beard at odds of 100/1. " EXPO The odds of the pair taking the plunge in Las Vegas are 500/1, while a wedding at Scotland's Gretna Green is an even longer shot, with odds set 10,000/1. Odds of the heir to the throne and his new wife honeymooning in space are 1,000/1. - EXPO