2016Prince William and Princess Charlotte look on as Prince George plays with a bubble gun at a children's party at Government House in Victoria, British Columbia, Canada, September 29, 2016. Reuters/Chris Wattie

Hollywood A-list actor Ben Affleck has opened up to the "The Graham Norton Show" about his unique experience with his youngest child Samuel while filming "Justice League" in London earlier this year.

"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," Affleck said during the interview (via E! News).

"It was pretty empty and then I noticed this weird vibe from the other grownups,” Affleck continued. “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 did not say if Kate Middleton and Prince William were also at the park.

Affleck said that Samuel came down with a cold after the impromptu playtime. "I can now tell him that he got a cold from the King of England!" he joked to BBC1 host Graham Norton. Affleck appeared on the talk show to promote his new film "The Accountant."

“We did all the sights and I wanted them to be cultured. Now if it was in America – and I hate to admit this – you’d get a VIP pass, you’d get backstage and they would accommodate you,” Affleck said in the interview.

“So I got a tour guide thinking this guy will accommodate me but that wasn’t the case! 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!”

He was also with estranged wife Jennifer Garner and their two children Violet and Seraphina while Affleck was filming the "Justice League."

In June 2015, Affleck and Garner announced their plans to divorce after almost 10 years of marriage.

"Life doesn't always turn out exactly the way you want. We're doing our very best and we're putting our kids first and that's how we're focusing on our day to day lives and we don't know what the future's gonna hold, but each step that we take is one where we prioritise our children and everything else comes second," Affleck told CBS This Morning. "She's just so good at doing that and has set such a good example and a lead that I follow. She's somebody that I admire and respect and remain excellent friends with."