Whilst the Hollywood bunch party it up in Cannes for the 67th Film Festival, there was a thoroughly regal affair closer to home at Windsor Castle as Prince William held a dinner to celebrate the work of The Royal Marsden Hospital. The elegant soiree was sponsored by Ralph Lauren, who has announced he will be funding a brand new breast cancer centre at the hospital. The exceptional number of A-list guests were dressed head-to-toe in Ralph Lauren, who greeted guests alongside the Duke of Cambridge, who is the president of the Chelsea situated hospital. Guests included infamous models Kate Moss and Cara Delevigne, Actresses Cate Blanchett, Emma Watson, Benedict Cumberbatch, Margot Robbie and Downton Abbey stars Lily James and Laura Carmichael. It seems the only person missing from the A-list event was the Duchess of Cambridge, of whom Prince William immediately apologised for her absence to the Laurens, saying: "I'm sorry my wife's not here, you probably would far rather you saw my wife." The designer clad guests first enjoyed drinks and a meet and greet with Prince William in the historic Waterloo Chamber before moving on to an extravagant dinner in the Great Hall. Whilst in sunny Southern France the beginning of the Cannes Film Festival kicked off with red carpet attendees including actresses Nicole Kidman, Blake Lively, Zoe Saldana and model Karlie Kloss. Check out the best dressed guests at Cannes so far and tell us in the comments which event you'd rather attend - a glamorous dinner with a Prince in a castle or a red carpet premiere with the creme de la creme of Hollywood elites? All the best dressed guests at Windsor Castle: