Prince William and his wife Catherine on Sunday attended the British premiere of Steven Spielberg's new film War Horse along with 600 serving and ex-serving military personnel and their families.
Spielberg said it was "an honour" to be attending his first royal premiere with the Duke and Duchess as he made his way in the rain down the red carpet at London's Leicester Square.
The US director also praised the couple's "wonderful" gesture to invite soldiers to the event.
"It's a great honour that they've (William and Kate) given up their time and also given up their charity and it's wonderful because it was their idea to bring the veterans here, so they could share this evening," he said.
The movie tells the story of Joey, a horse raised on the English countryside who is torn away from his home -- and stable lad Albert -- and sent to France to the battlefields of World War I.
The story follows Albert on his mission to find his equine partner amid the blood, mud and misery of the Great War.
Spielberg used celluloid film to record the movie, which received a Golden Globe nomination this month ahead of its Christmas Day release in the United States, to give it an old-fashioned feel.
The Hollywood heavyweight said filming the movie was "a beautiful, beautiful experience."
"All these actors, every single one in this movie bonded with Joey," he added. "If I could do it all over again, I would only do it again so I could repeat the experience."
Joey was played by around a dozen horses from all from around the world, notably Spain. Stable boy Albert is played by 21-year-old British actor Jeremy Irvine, who had previously only worked in TV.
The movie, which follows on a hugely successful Broadway and West End show, also features Sherlock actor Benedict Cumberbatch, Emily Watson and David Thewlis.
Most critics so far have been broadly positive, although some have questioned Spielberg's approach, like the Guardian's newspaper critic Andrew Pulver, who said the director "can't seem to snap out of a now-habitual mode of vitality-erasing, dewy-eyed affectation."
The Duke and Duchess attended in aid of the Foundation of Prince William and Prince Harry, the charity set up by the royal brothers in 2009.
The servicemen and women invited to the premiere came from the Duke's regiments.