Judi Dench and Steve Coogan in Philomena. (Pathe)

The Lost Child of Philomena Lee was published in 2009, a book by journalist and writer Martin Sixsmith that told the incredible true story of a retired Irish nurse looking for the son that was taken from her by nuns when she was a teenager at a catholic convent in the 1950s. Now adapted for the screen by Stephen Frears (Dirty Pretty Things, The Queen), Philomena is an engrossing if sentimental crowd-pleaser starring Steve Coogan and Judi Dench in the leading roles.

Coogan, who produced the film and co-wrote the screenplay, gives a superb performance as Sixsmith, the once esteemed journalist who is in need of rehabilitation after being unceremoniously sacked from his job as Labour's director of communications. An intelligent but arrogant individual, as a former correspondent in Washington and Moscow he at first sees Philomena's story as below his skillset, before journalistic intrigue arouses his curiosity and he agrees to help her find her estranged son for a newspaper article. He's not the most likable figure, but Coogan's nous for comic timing means the tone is never too serious, and his determination to help her endears him to us. Fallen from his high perch back down to Earth, as Philomena tells him, "their loss is my gain".

Dench is similarly sublime as Philomena, bringing immense warmth to the screen as the little old working-class lady with a heart of gold. From playing M in the Bond series to Queen Elizabeth in Shakespeare in Love, she's known internationally for playing ice cold matriarchal roles. But as Philomena Lee she plays a benevolent figure who's never questioned the harsh treatment she received whilst growing up in Ireland.

They make a dynamic odd couple, the warm and humble demeanour of Philomena complimenting the snarky and cynical Sixsmith. Using flashbacks and real Super 8 footage to flesh out the story, their journey is one that takes them from England to Ireland to America, unfolding revelations along the way.

Most biopics suffer from the problem that the story is more interesting than the characters themselves, but here you're invested as much in investigative journalist Sixsmith as you are Philomena. This isn't just the smart reporter helping the meek Philomena on her quest; he needs her as much, if not more, than she needs him. Here is a man who after playing with fire in Westminster ended up with his fingers very badly burnt. Mired in politics for far too long, it's only through meeting Philomena that he realises the effect the state and religion has in shaping ordinary people's lives, for better or worse.

There's nothing profound in such an examination, and it's also not unique, with Peter Mullan's excellent movie The Magdalene Sisters already chronicling how teenage girls suffered at the hands of the Catholic Church in Ireland at their now-notorious asylums. It's a little too neatly packaged as a box office crowd-pleaser to leave a lasting impression, but as a touching film about faith and forgiveness it still manages to pull the heartstrings come the very end. Like the chick-lit that Philomena reads, this is a movie not made for high-brow audiences, but a sentimental crowd-pleaser that is sure to open up her incredible story to a wide audience. I can forgive it for that.

Philomena is screening as part of the 2013 London Film Festival. The film will be released in UK cinemas nationwide from 1 November.

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