Camilla and her husband Prince Charles were the guests of honour at the screening of the film, a thought provoking and intimate tale of mortality and mourning based on the best-selling book of the same name.
It was also big night for the movie's young star Saoirse Ronan, who was delighted to be introduced to the royal couple.
As she strolled the red carpet in a grey chiffon dress and a glam up 'do it was plain to see how much the American-born Irish actress has blossomed into a poised young lady since she was nominated for an Oscar for her role in 2007's Atonement.
Saoirse said making the new high-profile film had been something of a "nerve wracking" experience.
But the whole thing was made easier with the support of her co-star Susan Sarandon, who she said became like a "mother" to her during filming.
"She's very maternal on the set. She did look after me," says the teenager of Susan, who was also at the screening.
"And she's a very open person so it was nice to be with someone like that."