The English actor seems to have suddenly morphed into a 25-year-old, with Twitter users left in disbelief after his friend and former co-star Emma Watson posted a picture of him in BBC3 drama Bluestone 42.
"Always said you were my favourite," Lewis replied, as "Neville Longbottom" immediately began trending.
Bluestone 42, about a group of soldiers serving in a bomb disposal detachment in Afghanistan returns for a third series on Monday at 10pm, and there are no wands or pet toads in sight.
Lewis has appeared in The Syndicate, The Rise and The Sweet Shop since the final Harry Potter film, Harry Potter and the Deathly Hallows: Part 2 reached cinemas in 2011.
His latest photo sees him looking rugged and “very serious” in army uniform, but Lewis insists that fangirl crushes was “never something [he] associated with [himself], ever”.
“I wasn’t attractive when I was growing up and I don’t think I am now,” he told The Mirror in 2012. “It was never, like, ‘Let me takes these ears off then you’ll see’.”
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