William reacts as Brad Pitt jokes he will name his Bafta Harry

Margot Robbie joked that Brad Pitt would be naming his Bafta award Harry because "he is really excited about bringing it back to the States" – as the Duke of Cambridge watched from the audience.

With Pitt not present at the ceremony in London, Robbie stepped up to collect the award for best supporting actor – for his role in Once Upon A Time In Hollywood – on his behalf.

Reading Pitt's words from a sheet of paper, Robbie, his co-star in the Quentin Tarantino movie, closed the acceptance speech by saying: "Oh, and he says that he is going to name this Harry because he is really excited about bringing it back to the States with him."

As the audience reacted, she added: "His words, not mine."

Harry's brother William, watching from the front row alongside the Duchess of Cambridge, appeared to enjoy the joke as both he and Kate were seen laughing.

The Duke and Duchess of Sussex announced recently they would be stepping down from their royal duties and bringing up son Archie mostly in Canada.

In his speech, read by Robbie, Pitt also joked about Brexit.

Robbie began: "He starts by saying, 'Hey Britain. I heard you just became single – welcome to the club'."

Pitt's award was his first ever Bafta in an acting career that has spanned more than 30 years.