THE Duchess of Cambridge kicked off her 30th birthday celebrations by attending the glitzy premiere of War Horse – the Steve Spielberg epic filmed partly on Dartmoor.

Kate, who celebrates her birthday today, shared the red carpet with the film’s equine star.

Devon author Michael Morpurgo, whose children’s book inspired the film, led the well-wishes for the Duchess.

Kate, who attended the premiere with the Duke of Cambridge, shared the red carpet with the equine star of the film. She grinned and laughed when she spotted thoroughbred Joey standing patiently outside in the rain.

Mr Morpurgo said it was an “honour” that the Duchess chose War Horse as her first royal premiere and said he would send her a copy of the book as a birthday gift.

The premiere of Steven Spielberg’s film, in London’s Leicester Square, was also attended by 600 serving and ex-serving military personnel and their families, as well as beneficiaries of military charities.

The Apollo Cinema at Paignton, where the film receives its first local showing tonight, has launched a free ticket offer for military personnel.

The royal couple went to the event in aid of the Foundation of Prince William and Prince Harry, which helps the welfare of those in the Armed Forces.

The First World War epic, which was nominated for best drama at the Golden Globes, follows on from the success of the play, which debuted at the National Theatre in London in 2007 before sell-out West End and Broadway runs.

The film largely met with a thumbs-up from newspaper critics today, with reviewers in both The Times and the Daily Express awarding it four out of five stars.

The Independent, meanwhile, gave it three out of five stars.

War Horse opens in cinemas on Friday.