The Duchess of Cambridge, wearing a red Alexander McQueen dress she last wore on the royal barge during the Diamond jubilee, met with iconic actors including Dame Helen Mirren, Ralph Fiennes, Helena Bonham Carter, Alan Rickman, Uma Thurman, Joan Collins and Sir Roger Moore, on a night celebrating the Queen's 60 years as patron of the Royal Academy of Dramatic Arts (RADA).
After watching a series of short performances alongside the Queen, including a medley of songs from Oh What A Lovely War, Kate caught up with Dame Helen, who was presented a fellowship at the BAFTAs on Sunday by Prince William. "My husband called you granny last night," she giggled.
"How delightful she was. Very sweet," recalled Helen, who had earlier recited a speech from Shakespeare's The Tempest as part of the evening's entertainment.
The actress was also congratulated by the Queen as they chatted in the White Drawing Room. Despite playing the monarch on both stage and screen, Dame Helen insisted her royal roles didn't come up in conversation.
"You're thinking 'it's the Queen, it's the Queen'," she said, and asked whether she still got star-struck replied, "Of course, even more so I think because I feel self-conscious, you know.
"I am genuinely always astounded by her aura, her twinkle, her presence. It never fails to surprise me, and again it's what everyone says when they meet her — it was what overwhelmed me the first time I met her."
Some of Hollywood's biggest stars were also humbled by the event. "It's such a privilege, such an honour," Uma Thurman said, adding of the spectacular setting, "It's so beautiful, I had to remind myself not to trip because you can be taken in by the beauty of the place."
The invitation to the Palace was a defining moment for Gemma Arterton too. "My mum and dad were so proud when I got the letter. They said, 'You're going to meet the Queen!'. I've met most of the royal family, but I'd never met the Queen. Now I've got the full set!"
Among the 250 stars at the glittering reception were Dame Angela Lansbury, director Steve McQueen and Jane Horrocks, who were among the line-up of 10 handpicked celebrities chosen to meet the Queen in the drawing room before she moved into the ballroom to mingle with the rest of her guests, including Mike Leigh, Michael Sheen and Harry Hill.