The 23-year-old actor, who plays bad boy Draco Malfoy in the franchise, said that as the time to say goodbye drew near, he couldn't help but feel overwhelmed.
Speaking to the Washington Post, he said, 'It was very weird. Nobody knew what to say. I kinda shook everyone's hands and said thanks to everyone and ran off before I got too emotional.'
He praised the decision to split the final instalment into two parts because it ensured that none of the narrative was lost.
He added, 'It's a brilliant choice. One of the things that we had to do was stay true to the story that was so beautifully told by J.K. Rowling.
'If we had cut out half of the book, it would have caused such uproar with fans. It really is two separate stories, the build-up, and then the battle.'