Dame Judi Dench has revealed that there was a lot of laughter on the set of Philomena, despite the heavy subject matter.
Stephen Frears' drama follows the story of Irish single mother Philomena Lee - played by Judi - as she searches for her son she was forced to give up for adoption in the 1950s by the nuns who ran an Irish convent where she gave birth.
"We just laughed so much. If you're doing something very responsible and serious, the more you kind of laugh away from it, the more concentration you can apply to it," she admitted.
The actress referred to her starring turn in Trevor Nunn's adaptation of Macbeth in 1976.
"When I played Lady Macbeth with Ian McKellen, the level of humour was beneath children, beneath childish humour before we went on, all of us, the whole company," she recalled.
"Once we got rid of all that, we were able to get on and be really concentrated on what we were doing. It's actually nervous energy you must get rid of. Once you do that, somehow something calms down and you get to the essence of something. The more of a tragic story you tell, the more you have to laugh in a way to balance it out."
Judi, best known for playing M in the James Bond films, is glad she met the real Philomena before filming started.
"It's very difficult (to portray a real person). Queens Elizabeth I and Victoria, Iris Murdoch, and now Philomena, who is very much with us, is ever-present and so one's concern is to do credit and justice to the person you're playing," she said.
"I wanted to meet her. We met for lunch just before we started filming," she said.
Philomena opens in cinemas on November 1.