Quiet 30th birthday for Prince William

Prince William marked his 30th birthday with breakfast in bed served by wife Catherine in a low-key celebration for the future king. The Duchess of Cambridge gave the second in line to the British throne a bespoke watch before William began his fourth decade on Thursday by heading off to work on a RAF training course, The Sun newspaper reported. Close friends of the prince are due to gather for dinner on Saturday night, with guests asked to bring a prop and make a brief speech about William. \"She\'s spent weeks planning this,\" a friend of Catherine\'s told The Sun of the dinner. \"William can\'t believe he is 30 so Kate wants all his old friends there.\" Prince Harry is understood to have lent a hand in planning the evening. As the Queen and other senior royals enjoyed a day at Royal Ascot on Thursday, William\'s milestone saw him inherit STG10 million ($A15.6 million) from the estate of his late mother Diana, Princess of Wales.