"As I've known Emma for so long, I reckon it will be 10 times worse," says the 20-year-old actor, who plays Ron Weasley.
"I really love the seventh book, but there is no way it will be tame with the Hermione stuff."
"I don't think it's quite up there with Dan's Equus, but it was quite a surreal experience, especially as we were sharing the bed with half a dozen camera crew," he says. "But, yeah, I was quite nervous, I think we both were.
"It was a new thing for the two of us – though, weirdly, I remember Kim and I doing a crossword in between takes. That definitely took our minds off the deed." He now hopes that Emma, 18, who plays the brainy Hermione Granger, will be similarly distracted. "I'll have a stack of crosswords at the ready," he says. To read the entire interview, click here