Princess Beatrice is gearing up to celebrate her 25th birthday on Thursday 8 August, and has invited a host of famous faces, including Prince Harry, Pippa Middleton, Ashton Kutcher, Robbie Williams and Sir Richard Branson, to her star-studded bash.
The young royal's sister, Princess Eugenie, and their mother, Sarah, Duchess of York, have reportedly been delegated as party planners, and have made sure the theme is a true reflection of Princess Beatrice's sporty personality.
"Guests have been told to bring trainers as the agenda for the evening involves outdoor games, followed by a big dinner," an insider told MailOnline.
Princess Beatrice, a keen runner who completed the London Marathon in 2010, will no doubt be encouraging her friends to enter into some light-hearted fun and games. The guests will then be rewarded with a feast at the Royal Lodge in Windsor Great Park.
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Topping Princess Beatrice's guest list will be her long-term boyfriend Dave Clark, who has been dating the royal for six years.
The young couple escaped London for some time over the summer and were most recently spotted relaxing on a yacht and enjoying quality time with friends in St Tropez.
The 24-year-old princess then travelled to Venice to holiday with her mother and sister, and the trio were seen enjoying a boat ride and dinner date with supermodel Kate Moss and her daughter Lila Grace. It is unknown whether Kate will make Beatrice's birthday party.
Prince William and Kate Middleton will be the most notable absentees from the celebrations, as the Duke of Cambridge will be working in Anglesey where he is stationed as a search and rescue pilot, while the Duchess is thought to remain at her parents' home in Berkshire with newborn Prince George.
Ashton Kutcher, a close friend of Princess Beatrice and Dave, has also been invited to the star-studded bash. The Hollywood star attended the royal's 18th birthday party with his then wife Demi Moore, and has enjoyed a close relationship with Beatrice and Dave in recent years.
Ashton and his girlfriend Mila Kunis were recently spotted enjoying a double date with the couple at London's Duck and Waffle restaurant, followed by drinks at Callooh Callay bar in nearby Shoreditch and Islington's John Salt bar.