Here’s the Harry Potter effect. Fans of the hit wizard series braved the pouring rain to catch a glimpse of their favourite stars at the London premiere of the new film.

Devotees were left undeterred by the weather, and gathered in the early hours of the morning at Leicester Square, where they were seen cheering and waving banners for the cast of ‘Harry Potter And The Half-Blood Prince’.

Jason Isaacs, who played villain Lucius Malfoy in the earlier films, said that he was barely surprised by the fans'' dedication.

"Frankly I think they would turn out in earthquakes and tornadoes. That's the effect the Harry Potter stories have. A lot of people have tried to understand why but nobody really understands – it's magic," the Telegraph quoted him as saying.

Stars walking down the soaked red carpet included Emma Watson, who plays Hermione Grainger, celebrity chefs Gordon Ramsay and Jamie Oliver with their families, Clive Owen, Graham Norton and Gary Lineker.