The Argo actor has been spending time in London shooting the upcoming Justice League movie and when his three children Violet, Seraphina and Samuel came to visit he took them to tourist hotspots such as Buckingham Palace, the Tower of London and Windsor Castle.

They didn't see any members of the Royal Family during those trips, yet he unwittingly ended up spending time in the presence of the Duke and Duchess of Cambridge's children, Prince George, three, and Princess Charlotte, 18 months, when he took four-year-old Samuel, four, to a children's play area.

"When it was raining I took my youngest to one of those kid’s indoor play parks," he explains to U.K. host Graham Norton. "It was pretty empty and then I noticed this weird vibe from the other grownups. 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. I can now tell him that he got a cold from the King of England!”

Ben, who plays Batman in the recent DC comics movie adaptations, also admitted that during their sightseeing tour he was hoping to score a VIP pass like he would in America, but he was treated like everybody else and couldn't get a decent space to watch the Changing of the Guard ceremony at Buckingham Palace.

"I got a tour guide thinking this guy will accommodate me (as a VIP) but that wasn’t the case!" he said. "He took us to the middle of the street but we were so far away not only couldn’t we see the guard, we couldn’t see the fence! We were surrounded by 50,000 tourists looking for selfie opportunities and we never saw the guards change! It was a disaster!"