Harry Potter star Emma Watson turned on the magic with a barely-there dress as she bewitched fans at the premiere of the latest Harry Potter film.

The actress showed a marked contrast to the prim and elegant outfits she has worn at the six previous Potter first nights, with a skimpy black lace mini-dress with a feathered skirt.

Watson, 20, who stars as Hermione Grainger in the wizard series, met some of the devoted and damp fans who had camped out for hours in London's Leicester Square for the occasion.

She was joined on the red carpet by Harry Potter And The Deathly Hallows Part 1 co-stars Daniel Radcliffe and Rupert Grint, who both wore smart suits for the launch.

The actress had earlier talked about her sense of style and how she had loved to choose her outfits from a young age.

She said: "My dad was very good when I was younger. He always encouraged me to choose things for myself. I was never just given clothes.

"From around six or seven, he would let me choose what I wanted to wear, so I always had my own identity. I have held onto that very strongly and refuse to be told what I should wear. If stylists work with me, they never just give me a dress and I'll put it on.

"I have always had a strong sense of self and my convictions."

This year's premiere seemed to break the "curse" of Harry Potter which has seen a number of previous launches lashed by rain.

Despite earlier downpours, the weather held off as Radcliffe (who plays Potter), Grint (Ron Weasley) and Watson arrived.

The story, the final Potter tale by author JK Rowling, has been split into two with the second film being screened next year.

Deathly Hallows is being released in UK cinemas from November 19.