But, speaking to Jonathan Ross, the former child star revealed that she was heartbroken because her love for the young actor - who played naughty Draco Malfoy - was unrequited.
She said: "Between the ages of 10 and 12 I had a crush on Tom. I used to go into work in the morning and look at the call sheet to see if he was going to be in every day. He was a bad guy, a few years older than me, and had a skateboard and that did it for me.
"He totally knew but said he only saw me in a sisterly way and that broke my heart."
But Emma scotched rumours that she'd had a romance with her other co-stars Daniel Radcliffe or Rupert Grint.
She continued: "There was no romance between me and Daniel or Rupert. The whole 10-year period I never so much as pecked one of them on the cheek.
"Rupert gave me a beaver when we all left. He sponsored a beaver for me for a year."
Emma recently commented on speculation about her appearing in the movie version of Fifty Shades Of Grey.
Emma's interview can be seen on The Jonathan Ross Show on ITV1 this evening.
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