The Duke of Cambridge invited over 200 notable figures into the royal residence in support of London's The Royal Marsden hospital, of which he is president.
Among the famous faces who filed into the benefit at Queen Elizabeth Ii's residence were Blanchett, Moss, Watson, Cara Delevingne, Benedict Cumberbatch, photographer Mario Testino, Helena Bonham Carter and singer Emeli Sande, who also performed at the event.
Fashion designer Ralph Lauren was the toast of the evening, with the prince revealing the style guru is funding a new state-of-the-art breast cancer research facility at the hospital.
The fashionable evening had one noticble absentee, however - Catherine, Duchess of Cambridge had stayed at home with their son, Prince George.
During the event, Bonham Carter admitted she was nervous about meeting Prince William again after a previous embarassing encounter.
She told reporters, "The Duke and I met before, along with the Duchess, before they were married, when I was staying on Mustique (island). I got very drunk at one point and I was determined to ask him to be a godfather to my daughter. He quite wisely said no. I admire him. He has got the same grace as both his parents."