Sienna Miller was excited to cancel 40th birthday party

Sienna Miller was thrilled to cancel her 40th birthday in December.

During an appearance on The Tonight Show Starring Jimmy Fallon on Thursday night, host Jimmy asked the British actress how she celebrated turning the milestone age.

Sienna revealed she had planned to throw a 1920s-themed bash, but had to can it at the last minute due to the Covid-19 pandemic.

"I have the worst birthday. I'm born on 28 December. I was driving this year, and the man said, 'Here we are in the black hole between Christmas and New Year - the 28th of December.' And I was like, 'No one's ever put like that.' But it's true! By the 28th, you're down," she sighed. "I was peer pressured to organise one, extensively, that I had to cancel because of Omicron. Not that that's a good thing, (but) it was ripping through England.

"Anyone who cancels on me is my favourite person."

Elsewhere in the chat, Sienna promoted her new drama series, Anatomy of a Scandal.

And while she has acted with some of the biggest names in Hollywood during her career, she admitted working alongside Amelie Bea Smith - the voice of children's TV character Peppa Pig - was a highlight.

"Bradley Cooper, Clint Eastwood... but whatever because I worked with Peppa Pig. I've never fangirled out on anyone, it was just - it was really too much," she smiled. "I'd sit there across set with my cup sort of staring at her. And then make her FaceTime my daughter relentlessly, and she was such a pro."