Image caption An emotional JK Rowling thanked fans and the cast at the premiere

A tearful JK Rowling said thank you to thousands of Harry Potter fans who packed London's Trafalgar Square on Thursday at the world premiere of the final film.

Despite torrential rain earlier, the sun shone down as stars of Harry Potter and the Deathly Hallows: Part II spent more than three hours signing autographs.

Daniel Radcliffe, who has played the boy wizard since he was 11, told fans the films would be with them "for the rest of their lives".

Speaking from a stage next to Nelson's column, Potter creator Rowling thanked the actors for "the amazing things they did for my favourite characters".

Media playback is unsupported on your device Media caption Daniel Radcliffe: "I'm just so proud of this last Harry Potter film"

Turning to the fans, she said: "Thank you for queuing up for the books for all those years, for camping out in a wet Trafalgar Square."

Fans back chanted "Thank you!" and Rowling said: "No, no, I'm already crying."

Radcliffe, who had earlier flown in from New York, said that Harry's story would never end.

"Each and every person, not just here in this square but around the world who have watched these films for the last 10 years, they will always carry the films with them for the rest of their lives," he told fans.

Michael Gambon, who plays wizard Dumbledore, told the BBC he was sad that it was all over and expressed "astonishment" at the reception.

Image caption The premiere took over the whole of Trafalgar Square

Rupert Grint, who plays Ron Weasley, thanked the screaming fans saying making the films had been "the best part of my life".

Grint and co-star Emma Watson spent hours on the red carpet signing autographs.

And Clemence Poesy, who plays Fleur Delacour, said: "I'm overwhelmed by it all."

Critical praise

Fans from across the UK, and as far as China and Argentina, were in Trafalgar Square to see the cast. Many had been been staking out their spot beside the enormous red carpet since Monday.

As the stars walked the carpet, fans thrust out copies of the final Potter book to be signed.

Many were dressed in Hogwarts robes and bore lightning flashes on their foreheads.

Others waved placards reading "We're all potty about Potter", "Potter 'til I die" and "Harry Potter is over. See you in therapy".

Other cast members on the red carpet included Robbie Coltrane (Hagrid), Tom Felton (Draco Malfoy), Jason Isaacs (Lucius Malfoy), and Julie Walters (Molly Weasley).

The carpet - which stretched three-quarters of a mile (1.2km) from Trafalgar Square to Leicester Square where the film was screened - is believed to be longest in the world.

Media playback is unsupported on your device Media caption JK Rowling on the "extraordinary" send-off for the Harry Potter films

Leicester Square, where premieres traditionally take place, is currently undergoing extensive renovation.

The entire Potter film series has so far earned more than £4bn worldwide.

It has been 10 years since the first movie in the series, Harry Potter and the Philosopher's Stone, which made stars of its young cast, Radcliffe, Watson and Grint.

Critics have so far praised the eighth film, with The Sun newspaper saying "the final instalment is still brimming with the old Potter magic".

The London Evening Standard saved its highest praise for the film's technical achievement, calling the special effects "the real magic, and perhaps our last authentic industry".

Harry Potter And The Deathly Hallows: Part II is released on 15 July.