The Gossip Girl star, who appeared alongside Helen in the movie Catherine the Great, revealed how the pair shared a steamy scene together.
But despite admitting to being slightly starstruck, the 26-year-old, said it’s all ‘part of the job’.
He said: “In everything I have done thus far I have had to do at least a kissing scene. I did Catherine the Great and had an intimate scene with Helen Mirren.
“I’m fine with it.
“Obviously, you do think, ‘It’s Dame Helen Mirren!’ But she was so down-to-earth, so funny, such a pro and so talented.”
Thomas also told how he is is extremely popular with the ladies because he is often mistaken for fellow Scots actor Richard Madden.
He said: “I always get mistaken for Richard Madden. It’s so embarrassing. It first happened when I was in a Starbucks in Burbank and a girl was like, ‘Oh my God! Are you who I think you are?’ I was like, ‘Yeah, yeah, it’s me.’
“She asked for a photo and I was said, ‘Yeah, of course you can.’
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“I was doing the whole thing, getting a photo taken, but then she said how she l loved me in Game Of Thrones! I didn’t know whether to say, ‘Wait, no, that’s not me!’”
He laughs: “It was so embarrassing that in the end I just decided to be Richard Madden.”
Thomas stars as Max Wolfe in the new reboot of hit show Gossip Girl.
The show takes place eight years on, with a fresh generation of New York private school teens under the surveillance of an anonymous Gossip Girl.
Thomas is best known for his roles as Sean Matthews on the Disney Channel’s The Lodge and as Harry Hook in the Descendants film franchise.
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