In the film, terminally ill Marion gains courage by continuing to sing in a local seniors' choir, with Arterton's Elizabeth eventually convincing Stamp's crotchety Arthur to take her place. Arterton loved working with Redgrave and Stamp. "I've acted alongside some legendary actors, such as Judi Dench, and the great thing about them is they're so normal. These days so many films are about young people when we've got all these amazing actors who don't get to show how good they are."
Stamp was impressed with his co-star. "When we were working on the movie Gemma turned down a huge lead role and I said, 'Why?' 'It's rubbish, not good for my career!' she replied. And I thought how wonderful is that. She is all of 23 or something, [Arterton is 27]. It was thrilling to work with those two women, I can tell you. It was like two different rare materials. I think it was the most challenging job I've ever done in movies," admits Arterton. "It helped that I sang in choirs in my childhood and teens, and for the movie I had to learn to play the piano in a month and conducting proved a challenge too.
Although Richard Scott was in charge of the choir, I felt a huge responsibility as they were mostly non-actors from the Newcastle area and I wanted them to sound good."
Song for Marion is set in London, not far from the housing estate in Gravesend, Kent, where Arterton was raised after her mother divorced her father when she was five.
Her mother, a keen music lover who worked as a cleaner, encouraged her academically gifted daughter to sing and perform. At 16 Arterton left school to attend Miskin Theatre School in Dartford and later received a scholarship to study at the top British acting school, The Royal Academy of Dramatic Arts (RADA) graduating in 2007. Perhaps she could be seen as a female Billy Elliot, a working class prodigy? "I don't know about a prodigy but I was very lucky. Not so much now but when I was a student we had a lot of support in the arts in the UK, especially if you came from a working class background."
Even if Arterton is currently one of Britain's most famous stars she is still acutely aware of the working class stigma. "I haven't completely gotten over it," she admits. "When I was training I definitely had that hang-up, but now being from a regional place as an actor is a good thing. At RADA one of the teachers told me, 'don't lose that because it's the most attractive thing'. I met Andrea Arnold and she's from the same town as me and she only works with people who are untrained. There's now a pre-conception that trained actors are stiff and not in contact with the real world. In the end you just have to take people's judgments with a pinch of salt. I was very lucky because I had the right people around me and the right parts came up."
Seemingly overnight Arterton splashed on to the film scene in St Trinians (2007) and Quantum of Solace (2008) and was hailed as the next big thing. Stephen Frears cast her in the sexy feisty title role in the romantic comedy Tamara Drewe (2010) though she took a step back with the 2010 flop Prince of Persia, which she thought had destroyed her career. She recently toured the world promoting Hansel and Gretel: Witch Hunters, together with a less enthusiastic Jeremy Renner and though she defends that disappointing blockbuster her focus now is on quality movies. In June she is alongside Saoirse Ronan in Neil Jordan's fantasy thriller, Byzantium, and she stars with Ben Affleck and Justin Timberlake in the crime thriller Runner, which releases later this year.
"I like taking risks but that doesn't always mean success," she says. "I've learned what I like and what I don't like and my opinions have grown stronger, which I think is good. You have to be so opinionated in this industry."
• Song for Marion is in cinemas now.
