Dame Judi Dench has revealed that she agreed to star in Stephen Frears' Philomena, because it was a story that "had to be told".
The Oscar-winning actress portrays Irish working-class woman Philomena Lee, as she searches for the son she was forced to give up for adoption in the 1950s, in the true-life drama.
Speaking at the Venice Film Festival, where the movie had its world premiere, the 78-year-old called it "a shockingly terrible story" and said it "rightly should be told".
Judi met her real-life counterpart several times before filming, and admired her enduring faith and ability to forgive, which "is what makes her extreme, and makes the story worth telling," she said.
Steve Coogan plays journalist Martin Sixsmith, who accompanied Philomena on her journey and wrote a 2009 book, which itself has been a catalyst for thousands of "shamed" Irish mothers who similarly lost their children to come forward, and also co-wrote the screenplay.
He said the film needed some comic relief "otherwise it would be just a tragic, depressing story".
"The humour was important to lighten the mood, and sugar the pill. It was also important we didn't overdo it. I said, 'If I mug too much, or if my face becomes too animated, tell me to turn it down'," he added.
Philomena will be released in UK cinemas on November 1.