“My character Malacy [in 'Cherrybomb'] works at a leisure center in Belfast,” Grint explained. “It’s not really a proper job, but this girl Michelle is my boss’ daughter. She’s really exotic and fashionable and she gets his attention, along with his friend Luke, and she starts this crazy competition thing between them.”

“Usually, Malachy doesn’t get the girl,” Grint said. “Luke is more of the ladies’ man, but he’s a bit more dodgy. Malachy isn’t a geek, he’s a bit of a thug, but he starts off as basically a good kid. He goes to work, he has a good relationship with his parents, but he’s got some bad influences, so he gets into a bit of trouble.”

Grint got a “little love scene” that’s a little more adult than the one he had in “Driving Lessons,” he said, “which was quite awkward to film, with the whole crew watching. They’re in bed!” But the real adult subject matter, Grint said, is what happens afterwards — which he didn’t want to spoil. “It gets quite serious,” he said. “It gets a bit crazy. Really violent and out of hand and lethal at the end.”

“It’s a mishmash of all sorts of different accents,” he said. “I got the vocal coach to make me a CD of all the lines and I put that on my iPod, and that really helps, to learn the vowel sounds. Otherwise, I’d pick it up from the crew, since they were all local.”

Only having one week of rehearsals also put the pressure on. “On Harry Potter, we do a scene every few days, and this was like 12 scenes a day,” Grint said. “It’s a much tougher shoot, really, and quite tiring, but it’s good, to be at this much faster pace. I prefer it to the waiting around. You’re always moving about. And at least I’m playing such a cool, different character that I’ve never done before. It’s nice to get to act like you’re more confident, even for a little bit.”