"Bits of it [were difficult]. Lots of running around. I'm not very good with a sword. I nearly killed somebody, actually," Lewis told United Press International at a recent New York press conference. "It was tough, but I loved it. I like playing sports and I'm active anyway, so I was keen to work with the stunt team. ... This one was a lot of running and I don't like running. I don't understand people who run, so that was hard, but it was fun when you have explosions going off around you, you've got blood and... even though you're doing it at 2, 3 in the morning in the freezing English cold, it was great, every second of it. People kept saying: 'Are you tired? Do you want to take a break?' And I was like, 'No, man, let's keep going.' This is good. When you're a young man, a young boy, all you want to be is the action hero, the James Bond, and I get to do that for a bit and that was great."
Coming back to his ability to wield a sword, Lewis recalled a dangerous mishap that occurred when he swung the weapon and it unexpectedly broke apart.
"The sword came off of the hilt and just went about 30 feet in the air and I was just holding the hilt, looking terrified into the camera. It's a great outtake. But it goes up and, obviously, what goes up must come down and it came down amongst a load of children -- the last place I'd want it to go -- and, amazingly, it missed everybody. I don't know how. I was very thankful. If you see it in a museum and it's dented and bent, that's because I did that," he said.
Lewis, now 22, has played Neville, the titular wizard's loyal friend and fairly ordinary classmate at Hogwarts, throughout the eight-movie series, starting with 2001's "Harry Potter and the Sorcerer's Stone."
In the final movie, however, Neville faces down evil Voldemort and his minions and defends his friends in tremendous acts of bravery of which some people might not have thought him capable.
So, when did Lewis realize Neville was going to play such a pivotal role in the last installment of the fantasy film franchise?
"I was in bed, actually, when I was reading [that in the last book]," Lewis replied. "Because [author] J.K. Rowling had already told me a few years previously that she had just finished ['Hallows'] and she had written a rather exciting bit for Neville Longbottom and, yeah, I didn't really know what to expect, to be honest, and then I read the book and I remember suddenly sitting bolt upright in bed, thinking, 'Wow, that's going to be cool.' I knew Neville was special. I knew he had something to give in this last book, but I didn't expect it would be something as epic as that and then, naturally, immediately after the excitement calmed down, the immense pressure started to build and I realized it was going to be crucial. I'm a huge fan of the books and I know what these stories mean to a lot of people around the world and I wanted to make sure we got that right."
Lewis admitted he didn't have to act much to convey his character's fear in a scene in which Neville faces off with Ralph Fiennes, who plays uber-villain Voldemort.
"He just stared at me the whole time. Even when other people were speaking, his eyes never left my face and it was like he was studying me and I just went to pieces. I suddenly felt like I was in the hardest exam of my entire life and it was frightening," Lewis noted. "But it spurred me on. It gave me that extra boost and that kind of challenge, as an actor, is what you need, I think. I think actors are in their element when they're pushed out of their comfort zone. I don't know if it's any good, I have no idea. That's up for the audience to decide, but I know that I loved every single minute of it and being able to work one-on-one with Ralph, despite the pressure, despite the nerves, it was once of the greatest experiences of my life and I will never forget it."
"Harry Potter and the Deathly Hallows, Part II" is in theaters now.