Stepping out to show appreciation for the work of The Royal Marsden, a number of Hollywood stars attended Prince William's dinner party at Windsor Castle on Tuesday (May 13).

Emma Watson struck a pose in the beautiful gardens and joined fellow British stars including supermodels Kate Moss and Cara Delevingne , and actors Benedict Cumberbatch and Helena Bonham Carter.

Meanwhile, the lovely Margot Robbie rocked a gorgeous silver gown and mingled with her Aussie mate, Cate Blanchett.

Prince William gave a speech before dinner and thanked the hospital for its wonderful work, stating, "I am exceptionally proud to be president of The Royal Marsden, an incredible hospital and a world class cancer center carrying out groundbreaking work, influencing the treatment of cancer, both nationally and internationally.”

The Duke of Cambridge added, “I am enormously grateful to Ralph Lauren for his generosity and to all of you who so kindly support the hospital. You should know that what you do saves lives and gives hope to thousands of people.”