The stars of "Harry Potter and the Half-Blood Prince" are due to walk the red carpet at the film's premiere in London.
Grint said he would attend after recovering from a mild bout of swine flu. He said the illness was not severe and "just like any other flu I've had before."
The cast members plan to wear white ribbons in memory of Rob Knox, a young actor on the film who was stabbed to death in London last year.
The sixth Potter film sees the boy wizard and his friends battling evil Lord Voldemort — and facing raging teenage hormones.
The movie opens around the world July 15.
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