Hollywood director Steven Spielberg has revealed that Kate Middleton was moved to tears at the premiere of his latest film, 'War Horse.'

According to the renowned director, the Duchess of Cambridge, who attended the premiere of the World War One epic with her husband Prince William, wept as she watched the film.

Talking to BBC Breakfast, Spielberg said: "I was sitting next to her and all I know is at one point my wife, who was sitting to my right, right in front of my face she passed a Kleenex... I saw the Kleenex go across my face, arrive and stop but I didn't want to intrude on her experience watching War Horse so I never glanced over."

The Duchess, who turns 30 today and also celebrates her first birthday as a fully-fledged member of the royal family, rubbed shoulders with celebrities from across the globe at the premiere held at London's Odeon in Leicester Square.

She oozed sophistication and her floor-length black lace Alice Temperley gown stole the show when she attended last night's screening in support of the Foundation of Prince William and Prince Harry, which helps the welfare of the armed forces.

The film, which is based on a children's novel set before and during World War I written by British author Michael Morpurgo and published in 1982. It was later adapted for the stage by Nick Stafford in 2007 and was well received in the West-End and on Broadway.

It is the story of a young British soldier and his struggle to be reunited with his faithful horse on the battlefields of France.

'War Horse,' which opened in UK cinemas on 13 Friday is nominated for the Best drama award at the Golden Globes.

Meanwhile, London animal charity, The Blue Cross, has also launched an exhibition to coincide with the release of the film.