Awkward! Actor Ben Affleck admitted he didn't even recognise the royal children, Charlotte and George, when his own kids started playing with them at an indoor park.
Ben revealed his poor knowledge of the British monarchy while telling BBC's The Graham Norton Show about a family trip to London while he was filming Justice League.
The actor and producer, 44, said: "Despite going to Windsor Castle, Tower of London and Buckingham Palace, we didn't see one royal.
"Then when it was raining, I took my youngest to one of those kids' indoor play parks. It was pretty empty and then I noticed this weird vibe from the other grown-ups.
"They were all very well dressed and they had earpieces and I thought, 'For a kids' place this is tight security.'
"I was the very last person to realise that Prince George and Princess Charlotte were in there playing with my kid."
He added: "I can now tell him that he got a cold from the King of England."
Speaking about his latest film, The Accountant, Ben confessed that maths was also a tricky subject for him.
He told Graham: "I'm pushing my luck with my daughter's 5th grade homework.
"The director insisted the numbers were exactly right and I defy any one person to solve the maths in that movie!"
Ben was joined on the couch by actors Claire Foy and Matt Smith - who actually play young versions of the Queen and the Duke of Edinburgh in The Crown - as well as Sir David Attenborough and Sting.
The programme will be broadcast on BBC One at 10.35pm on Friday - the same day as the release of The Accountant in the UK.