Chris Pizzello / Invision/AP 1 / 16
Chris Pizzello / Invision/AP 1 / 16

Daniel Radcliffe of "Harry Potter" recently opened up to GQ U.K. about his secret struggle with alcohol, but Emma Watson wasn't really aware of her co-star's struggles.

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"To be honest, it's really not something that I genuinely know much about," she told David Letterman on the "Late Show" Monday night. "But as far as I know, he never took a sick day. He was like the most professional, amazing guy ever."

The actress said she and Radcliffe, 21, have a very different relationship when it comes to their consumption of "controlled substances."

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"I mean, yes, I have tried spirits! Of course, I've tried spirits," she said. "We drink at 18 in the U.K., but I'm actually legal to drink now in the U.S. It's worth mentioning. I'm 21!"

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Watson also confessed to getting "very, very drunk once in my life, as everyone has."

"I have been drunk, and I'll bow to that!" she exclaimed, standing up and good-naturedly bowing to the crowd.

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