When Ben took his children on a recent trip to London, he hoped to show them some of England's famous heritage, but he didn't expect to see them playing with the royal family!
Appearing on The Graham Norton show, the Hollywood actor revealed that his children had visited London and explored historical landmarks such as The Tower of London, Windsor Castle and Buckingham Castle.
'Despite going to Windsor Castle, Tower of London and Buckingham Palace, we didn't see one royal.'
But, as it turned out, spotting a royal would be much easier than he originally thought.
Ben, 44, went on to describe how as it was a classically rainy British day, he took his children to a play area only to find that Prince George and Princess Charlotte were in fact playing there themselves.
'Then when it was raining, I took my youngest [Samuel] 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.'
And it sounds like the little royals may have been feeling a bit under the weather, as Ben described how his son caught a sniffle from Prince George.
'I can now tell him that he got a cold from the King of England', Ben added.
Ben has three children, Violet, 10, Seraphina, seven, and four-year-old Samuel, whom he shares with wife Jennifer Garner.
Actress Jennifer, known for her roles in Hollywood blockbusters such as 13 going on 30, The Dallas Buyers Club and Elektra, married Ben in 2005. Sadly, the couple announced their split in 2015 but are yet to finalise a divorce.