The British actor returns as former Hogwarts professor Remus Lupin in the final film of the series, Harry Potter and the Deathly Hallows: Part 2.
When asked if he ever gets recognised out and about, Thewlis told Digital Spy at the world premiere in London: "I don't, it's really weird. I went to Legoland recently and nobody noticed me at all. It doesn't really impact on my life at all."
Thewlis, who made his debut as the Marauder in Prisoner of Azkaban, quipped: "Nobody knows who I am."
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Commenting on the scale of the event staged in Trafalgar Square, Thewlis described the premiere as a "cultural event" for fans of JK Rowling's best-selling series.
"They are everything," he said of the fandom. "With this particular film, it wouldn't be anything without the fans. No matter what you think about the films critically, it's all about this really. This is what defines this film. This is a cultural event; it's what these people are here for right now."
Additional reporting by Simon Reynolds.
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