Daniel Radcliffe - Daniel Radcliffe Clashed With Emma Watson On Potter Set

Daniel Radcliffe and Emma Watson regularly caused friction on the Harry Potter set by engaging in furious bust-ups and refusing to talk to each other.

The actor counts Watson as one of his closest friends, but admits his co-star infuriated him when they took opposing stances in their frequent debates.

He tells Britain's Radio Times, "Oh, God. We used to argue about everything. Religion. Politics. I remember one of the big arguments we had on the fourth film - we didn't speak to each other for a couple of days - was about... She was arguing about the Latin language, that nobody knows what it sounds like, what a Latin accent should be. And I was like, 'Yeah, but it's still spoken a lot in the Catholic church.'

"Such a w**ky argument, looking back, and it got totally out of hand. She was furious; I was livid."

But the Brit admits his brainy pal often got the better of him, adding, "I certainly would advise anyone, if you're going to debate with her, know your s**t."