Speculation is mounting that Princess Beatrice may announce her engagement to her long term boyfriend, financier Dave Clark, tonight, at a lavish party being thrown at Prince Andrew's home, Royal Lodge, in Windsor Great Park.

According to the Mail on Sunday's diarist, the guest list for Bea's 25th includes Robbie Williams, Sir Richard Branson, Ashton Kutcher, Pippa Middleton and Dizzee Rascal.

‘Guests have been told to bring trainers [athletic shoes] as the agenda for the evening involves outdoor games, followed by a big dinner,’ a source tells the paper.

William and Kate will not be present, with William on duty in Anglesey and Kate at her parents’ home in Berkshire with Prince George.