On the eve of her 30th birthday Kate Middleton dazzled on the red carpet of the War Horse premiere, wearing a full-length Alice Temperley evening gown, but when the lights went down at the screening, the Royal Duchess of Cambridge let her guard down and cried, according to the film's director, Steve Spielberg.

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, Spielberg told BBC Breakfast. 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 Royal couple looked gallant as Middleton walked down the red carpet in black lace shielded by her Prince from the rain. She wore her engagement ring and a delicate diamond bracelet and black clutch bag. Spielberg acknowledged the honor of the Royals attendance at the film, saying they represented an entirely new era in British royalty that has the entire world excited, the Daily Mail Reported.

'When they came to America, that was one of the most exciting events, I think, that we've enjoyed for some time, so it's such an honor to be here in the UK to be able to meet them and to be able to show them, and all of us, War Horse,' the director said speaking at the premiere.

The film's premiere was a star-studded evening attended by the likes of Emily Watson, Benedict Cumberbatch and Micharl Morpurgo, who wrote the book on which the film is based on. I am so honored that the Duke and Duchess have chosen this for their first royal film premiere, Morpurgo said, the Huffington Post reported.

Some 600 British Military Veterans also attended the Premiere. Prince Harry was also present. After the Premiere, Middleton was rumored to have attended a private birthday party organized by her brother-in-law and sister Pippa Middleton. A royal source told Grazia Magazine that the party had a 80s theme and took place in a secret location in London.

Kate Middleton
Britain's Catherine, Duchess of Cambridge arrives at the UK premiere of the film 'War Horse' in London January 8, 2012 Reuters
Kate Middleton
All eyes are on Kate Middleton and Prince William to have their first child, but the couple has decided to ease into parenthood by adopting a puppy. Reuters
Kate Middleton
Britain's Catherine, Duchess of Cambridge arrives at the UK premiere of the film 'War Horse' in London January 8, 2012 Reuters
Kate Middleton
Director Steven Spielberg (R) and producer Kathleen Kennedy attend the UK premiere of the film 'War Horse' in London January 8, 2012. Reuters
Kate middleton London United kingdom Kate middleton