Olivia Colman had a "slightly embarrassing situation" while shooting a sex scene with Micheal Ward.
The 48-year-old star was left feeling awkward when her 'Empire of Light' co-star revealed her was 25 while she was straddling him.
Speaking on the New Year's Eve special of 'The Graham Norton Show', she said: “There was one particular moment when I was astride Micheal in a compromising and slightly embarrassing situation and he said, ‘It’s my mum’s birthday today.’
“When he said she was 43, I was like, ‘Okay, stop talking!'”
Olivia - who played Queen Elizabeth II in Netflix's 'The Crown' - was director Sam Mendes' first choice for the role of Hilary Small in the 2022 British romantic drama.
She said: “Apparently it was. But Sam is so nice he would say that anyway. He was watching ‘The Crown’ at the time and thought of me.
“We had a Zoom conversation during lockdown and I said ‘okay, yes’ before I even knew what it was. It is an incredible accolade for him to write something for me.”
Olivia quipped: “It was an amazing part thank god – can you imagine if it had been rubbish!”
Micheal was blown away by how nice Olivia is and "learnt so much" from her.
He said: “It was an amazing experience. It was incredible just to share the same space. I learnt so much about being a real person – everyone had a real sense of humanity.
“If Olivia had been rude I might have thought that’s how I need to be to reach a certain level of success but the fact she is so lovely showed me I can be a good person and still be successful.”
'The Graham Norton Show', BBC One, Saturday 31st December 10.55pm. Also available on BBC iPlayer.