By Victoria Lindrea BBC News entertainment reporter

A trust has been set up by the film-makers to help local Kenyans

But 49-year-old Brazilian director Fernando Meirelles, who won Miramax backing for the much-lauded Brazilian film City of God in 2004, is still not satisfied.

"I don't want to see this film again," he told the BBC News website. "I'm happy with the film, but of course I would change hundreds of things."

"I never stop working on a film. I can't help myself."

The film, based on a best-selling John Le Carre novel, is the story of a British diplomat (Fiennes) whose wife is murdered when she threatens to expose the pharmaceutical companies testing drugs on innocent Africans.

I am more interested in doing smaller films that I can control Fernando Meirelles

Principally shot in Kibera, Kenya, the largest slum town in Africa, the film began as a political drama but ultimately evolved into a powerful and moving love story.

"When I first read the script, the political side of the story really interested me. I was interested in talking about pharmaceutical companies, and how corporations and government work together," Meirelles said.

"But then, watching the whole film, it was like hearing my own voice - like the director preaching to the audience. So I started to cut and in the end, I think it became more of a love story."

The rare opportunity to shoot a film in Kenya was all the more remarkable considering Le Carre's novel was originally banned in the East African country because of its depiction of corrupt Kenyan officials.

But the persuasive charms of British producer Simon Channing-Williams, whose films include the award-winning Vera Drake, won through.

The British film was shot on location in Kenya and London

"They didn't want us to shoot there in the beginning. But Simon is a great diplomat, and he explained to the Kenyan government that we were going to do the film anyway."

"And when they realised that shooting the film in Nairobi would bring some visibility to the country, some money and jobs, we had lots of support. "

The welcome the British film crew received in Kenya was returned in kind.

Producer Channing-Williams set to work making small changes to improve the lives of local Kenyans - installing water tanks, a new bridge and a classroom in Kibera, and a secondary school in the deserts of northern Kenya where the film concludes.

"I think, in the next two or three years, we are going to see a lot of films set in Africa, or about Africa," said Meirelles, who claims the poverty of Brazil's shanty towns pale in comparison to the poverty he witnessed in Africa.

"We forgot this continent for a long time - and now, finally Africa is being rediscovered."

He cites a number of Africa-led dramas in production, including The Last King of Scotland, from British documentary-maker Kevin Macdonald, based on the fall of Idi Amin.

Fiennes has praised Meirelles' "energy" as a director

"Everybody is more interested in political films now. Even the young generation are starting to talk about international politics - everybody is getting more involved."

For his own part, Meirelles is keen to keep his distance from the Hollywood studios.

"I am not planning on doing big studio movies, I want to do my own personal projects."

"If you do a film with a high budget, people want to control it. Marketing people tell you what to do, and where to cut, so they can get their money back. I am more interested in doing smaller films that I can control."

The film-maker plans to return to his native Brazil to complete work on a film script featuring seven stories from around the world about globalisation.

"It is not a political or sociological film, it is more philosophical - it is about happiness. What makes us happy and the choices we take in life."