Future National Theatre boss Rufus Norris has revealed he is about to start work on the film version of hit stage musical London Road.
Norris plans to finish the film this year before he takes over from Sir Nicholas Hytner as the National's artistic director in April 2015.
"It's a bit of a double whammy at the moment," Norris told the BBC.
"In a week I go into prep for my next film. So I'm trying to balance the two - which is keeping me up at night."
London Road, which Norris directed at the National Theatre in 2011, is about the community in Ipswich where five prostitutes were murdered in 2006.
It features writer Alecky Blythe's recorded interviews with the people of Ipswich set to Adam Cork's music.
After a string of five-star reviews the musical was revived at the National in 2012.
Norris said casting for the film was under way but it was too early to make any announcements.
"We're looking for actors who can sing without a doubt," he said at the London Critics' Circle Film Awards on Sunday. "The music of London Road is not like you would imagine in a musical.
"It involves a huge amount of craft, but not a huge pair of lungs. It's the musical discipline rather than years of belting it out on the West End stage that we need."
Norris said that filming would take place "within the M25" rather than in Ipswich "for all sorts of practical reasons".
"The actual residents involved in the film are all very much behind it - otherwise we wouldn't be able to do it," he went on.
"We are quoting them word for word so we need permission for every phrase of that.
"It will inevitably waken the whole debate up again, because it was a very deep tragedy and a lot of people's lives were affected by it."
Having initially trained at Rada as an actor, Norris has directed theatre in the West End and on Broadway and also has experience with opera and film.
He recently directed The Amen Corner at the National and created Dr Dee: An English Opera with Blur frontman Damon Albarn for the Manchester International Festival in 2011.
He made his first foray into film in 2009 with King Bastard, a short film about a young girl's grief for her grandfather.
His first feature Broken, which starred Tim Roth, Rory Kinnear and newcomer Eloise Laurence, premiered at Cannes in 2012 and was named best film at that year's British Independent Film Awards.