In 1968 Norman Lewis wrote an article called Genocide in Brazil. The photographs that accompanied it were by Don McCullin.

Lewis later said that this one piece of journalism was the great achievement of his life. It led directly to the creation of Survival International and a change in the law relating to the treatment of indigenous people in Brazil.

Lewis is known as a brilliant writer - one of our best, said Graham Greene, 'not of any particular decade of our century'. He's best remembered for A Dragon Apparent and Naples '44.

Don McCullin didn't travel with Norman Lewis to Brazil, but they struck up an unexpected friendship. He was like my father, the great photographer says.

And in Norman Lewis's later years they worked together in Venezuela, Papua New Guinea and elsewhere. But McCullin didn't read many of his books. "I struggled through Naples '44" he admits. Yet his admiration for the way Lewis opened his eyes to the world remains undimmed.

Recorded on location at McCullin's Somerset farmhouse with Norman Lewis's biographer Julian Evans.

Presented by Matthew Parris.

Produced at BBC Bristol by Miles Warde.

First broadcast on BBC Radio 4 in August 2017.