When Tessa walks through the slum, numerous children ask her "How are you?" and she responds "I'm fine, how are you?" That scene was unscripted. The children are actual children who live in Kibera, not extras.
Given the subject matter, the Kenyan Government of Kenya proved to be remarkably accommodating to the filmmakers. The Hon. Raphael Tuju, Minister of Information & Communications, stated: "The Constant Gardener is very critical of Kenya, and it was unprecedented that this ministry would support it and license it. But I went ahead and made sure that we did so, because if we didn't support it being filmed here it was still going to be filmed somewhere else, and it would still be critical of Kenya in the past, with respect to issues like corruption."
Fernando Meirelles lobbied to have the movie shot in Kenya, where the story is set, instead of in South Africa, where most of Africa's film industry is located.
Actor Danny Huston, cast in the film as the British High Commission's Head of Chancery, Sandy Woodrow, commented: "Modern diplomacy is all about business, and about trying to encourage commercial ventures. I also had a meeting in London with two gentlemen who shall remain nameless, since they worked for [British Secret Service agencies] MI5 and MI6. The more time I spent with them, the more I felt that they
actually were like the people portrayed in the book. They have an extraordinary, sometimes spectacular way of not answering a question you ask them."
Ralph Fiennes held and operated the camera for Justin Qualye's point-of-view shots. Fiennes is billed in the closing credits for "Justin Quayle POV Camera". As of August 2016, it's Fiennes' only credit in a camera department for a feature film.