A-listers galore descended on Windsor Castle on Tuesday night in what one royal-watcher has described as a "perfect" mingling of royalty, charity and celebrity.
Invited to the glittering gala dinner, hosted by the Duke of Cambridge to celebrate the pioneering work and fundraising of Britain's leading cancer hospital, the Royal Marsden, were Cate Blanchett, Emma Watson, Benedict Cumberbatch, Mario Testino and Helena Bonham Carter, as well as rock stars, city moguls and multimillionaire philanthropists.
American designer Ralph Lauren sponsored the event, which saw the launch of a new fundraising partnership between his company and the charity. Not surprisingly, fashion was very much a theme of the evening, with Vogue editor Alexandra Shulman, ubermodel Kate Moss and the model du jour Cara Delevinge among many female guests who were wearing dresses from the Lauren collection.
The Duchess of Cambridge, who is known to be a fan of Lauren, was unable to attend, but her absence is due to a policy for the couple to keep their charitable projects separate.
Guests mingled at a drinks reception in the historic Waterloo Chamber before a lavish three-course dinner in St George's Hall, where the singer Emeli Sande later entertained the 200 diners.
This, say some royal observers, suggests that the Duke intends to harness the global power of celebrity more effectively in his charitable and campaigning work than any royal before him.
The couple's "pulling power" in winning the support of the rich and famous around the world to their causes is perhaps only rivalled by the Obamas. The global coverage of their hugely successful three-week tour of Australia and New Zealand with baby George last month has cemented that status.
Royal biographer Penny Junor agrees William and Kate have achieved "absolute megastardom". "I think you have to compare them to William's parents, who didn't handle [their fame and celebrity] in quite the same way," she says.
"The reason they [William and Kate] are so successful is that they realise they are not average celebrities, and I think that's the key point. Celebrities have their moment of fame and then they disappear. This couple have got to be around, and not offending anybody, pleasing everybody, for the rest of their lives."