Following its successful adaptation of John Le Carre's The Constant Gardener, Simon Channing Williams and Gail Egan's London-based Potboiler Productions is preparing a new film based on Le Carre's latest book, The Mission Song.

Joe Fisher, writer of acclaimed TV drama Soundproof and of 1998's The Tichborne Claimant, is scripting the adaptation.

The budget range is likely to be in a roughly similar range to that of the $23m Constant Gardener.

The Mission Song is about an idealistic British (but Congo-born) interpreter married to an upper-class white English woman. The story is set in the Congo and in the UK.

'There continues to be this wonderful, burning sense of anger about his (Le Carre's) writing,' Channing Williams said of the novel.

Potboiler was shown an early copy of the book by Le Carre and eventually secured the rights to the novel against fierce competition.

The producers haven't yet appointed a director. 'We're at least a year away from filming,' Channing Williams said.

Unlike The Constant Gardener, which was filmed on location in Kenya, The Mission Song won't be shot in the Congo, which remains one of the most war-torn countries in Africa.

Channing Williams is hoping to put The Mission Song together as a UK-qualifying film using the new film tax relief. 'It will be a tougher call if we can't,' he said.

Potboiler is developing The Mission Song through its own, in-house development fund.

The news of the new Le Carre adaptation comes as Potboiler pushes ahead with two other projects. Later in the year, shooting is due to begin on Ralph Fiennes' $10m directorial debut feature Snow Country, written by Nicky Rohl. Set in the 1950s in Winnipeg and the Arctic, the film, about a 17-year-old Inuit girl in a convent in northern Canada, comes billed as 'both a tragedy and a love story.'

Rohl has also scripted another project for Potboiler, The Quickening, which Lee Tamahori is attached to direct.

Last week, Channing Williams (one of the founders of The Constant Gardener Trust in Kenya) was awarded the 'Order of the Grand Warrior' at the Kenyan Embassy in London. He is the first non-Kenyan to have received the award since ex-UN secretary-general Kofi Annan.

Le Carre has now agreed with his publishers Hodder that all the income from the new paperback version of The Constant Gardener will be going to The Constant Gardener Trust in perpetuity.