The 28-year-old star was introduced to the reigning monarch at the Gladiator II world premiere on Wednesday.
The historical epic picks up 20 years after the Oscar-winning original, and marks Mescal‘s first big studio movie after success in TV and independent film, playing Roman warrior Lucius Verus.
Talking about his brush with royalty on the red carpet of the film’s Los Angeles premiere on Monday, Mescal told US outlet Variety he did not see it coming.
He said: “How wild is it? It’s definitely not something that I thought was in the bingo cards.
“I’m Irish, so it’s not on the list of priorities”.
He then swiftly turned the answer to the film’s 86-year-old director, Ridley Scott, saying: “It’s an amazing thing for Ridley because I know how important that is for him.
“So, to see his film celebrated in that context was pretty special.”
Ahead of the premiere, both Mescal and Scott had enjoyed a champagne reception at Buckingham Palace, and so were already in a celebratory mood on their arrival.
Due to the large number of people at the event, Mescal admitted it was also hard to hear what was being said during his exchange with the King, so he was “nodding along and smiling”.
The world premiere was held in aid of the Film and TV Charity, which celebrates its 100th anniversary this year, and marked the first premiere Charles attended as King.
The King also met with Mescal’s co-stars including Oscar-winner Denzel Washington and Narcos actor Pedro Pascal.
Other celebrities to attend included actor Joseph Fiennes and TV presenter Claudia Winkleman.
Reviews of the film have been mixed thanks to its more-is-more attitude to CGI and OTT storylines, but there is broad agreement that audiences will leave the cinema somewhat entertained.
Speaking to Sky News at the London event, Mescal said being part of the movie was a “wildly… overwhelming” experience“.
Sir Ridley – who cast Mescal in the role after a brief Zoom chat with the actor – told Sky News his reason for choosing him was that he saw aspects of “a young Albert Finney” in him.
The original Gladiator starred Russell Crowe as Roman general Maximus Decimus Meridius. The Australian actor does not return for the sequel.
Joaquin Phoenix also had a starring role in the first film, which Scott later admitted he nearly walked out of.
Both Mescal and Scott have teased that they would both be up for a third film.
Gladiator II is in cinemas now.
