Was it the heart-wrenching story of a boy and his horse, or was it the fact that she was living the final few moments of her twenties? Either way, Kate Middleton was reaching for the tissue when she watched Steven Spielberg's War Horse at the film's London premiere on Sunday, one day away from her thirtieth birthday.

Spielberg said he became aware that the Duchess of Cambridge was tearing up but chose to let her keep her privacy. "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," the director told the BBC. "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."

Kate, who attended the premiere in a lacey Alice Temperley gown accompanied by her husband Prince William (pictured), is said to "be celebrating with family and friends" as she turns the big 3-0, according to Us Weekly.

Read more here:

Family Ties: Kate Middleton Related To Jane Austen

Kate Middleton Top International Best Dressed List

Kate Middleton’s Wedding Dress To Be Displayed