The team made three programmes about their experiences for the BBC’s Traveller’s Tales series, which was produced by David Attenborough. Cowell’s experiences on the Far Eastern Expedition did nothing to discourage him from joining the 1957 Oxford and Cambridge Expedition to South America. It was on this expedition that he first met the Villas Boas brothers. He was so intrigued by the brothers that he left The South American Expedition to join them on the Centro Geographico Expedition to find the geographical centre of Brazil. This was the beginning of a lifelong friendship with the Villas Boas and his introduction to life in a rainforest.
On return to the UK, Cowell became a reporter for the ITN current affairs series, Roving Report, which led him to many parts of the world. In 1962 he returned to South America to make the three part series The Destruction of the Indian (1962). This was followed by a two part series on the British explorer, Colonel Fawcett, who had disappeared in the Brazilian Amazon while searching for the city of Atlantis.
One of Cowell’s most renowned and poignant documentaries was The Tribe That Hides From Man (1970). Cowell and a small crew accompanied the Villas Boas brothers as they went deep into the rainforest in an attempt to make contact with the mysterious Panará tribe before a road was built through their territory bringing inevitable disease. The film was all the more poignant for the expedition’s lack of success. Cowell won his first BAFTA.
During the mid 1960s, Cowell began his investigations in Southeast Asia. Raid Into Tibet (1966) revealed Tibetan guerrillas’ resistance against the Chinese occupation of Tibet. In Southeast Asia Cowell’s exploration of the tribal politics of the opium trade in the Golden Triangle, especially in Burma, resulted in The Unknown War (1966) and The Opium Warlords (1974). During the making of this last film, he and cameraman Chris Menges were trapped in Burma for 18 months. In 1978 he returned to the region and made the three part series Opium, which uncovered the politics of the drug trade both in the Shan States and in the US. The Heroin Wars, a series of three programmes released in 1996, explained further developments in the war on drugs since Cowell’s initial forays into the region.
When not filming in Southeast Asia, Cowell was back in Brazil. By the late seventies he had spent almost twenty years fliming there and had become deeply concerned by the systematic destruction of the Amazonian rainforest. He persuaded ITV to back an environtmental film project. For the next ten years he and a permanent film crew chronicled the catastrophe of deforestation in The Decade of Destruction. He followed Chico Mendes, a friend and rubber tappers’ union leader, as Mendes battled against the ranchers who were encroaching upon the forest. Mendes was assassinated in 1988. Chico - 'I Want to Live' was released in 1989. Ten years later, Cowell was back in Brazil having finished The Heroin Wars. This time it was to make The Last of the Hiding Tribes, which looked at the plight of the few remaining uncontacted peoples. Cowell’s most recent documentaries also focused on the struggle to save the Amazon and its indigenous peoples: Fires of the Amazon (2002), for the BBC Correspondent series, and Jungle Beat (2005).
Cowell was a founding member of the company Television for the Environment and the charity Television Trust for the Environment, established in 1984 and collectively known as TVE. The enterprise produces films and encourages awareness about environmental issues. Among its core founders and providers are the World Wildlife Fund (World Wildlife Fund for Nature) and the United Nations Environment Program.
Cowell published three books recounting his experiences while on location (The Heart of the Forest, 1960; The Tribe That Hides From Man, 1973; The Decade of Destruction – the Crusade to Save the Amazon Rain Forest, 1990) and won numerous awards for his documentaries. Cowell is notable for his distinctively anthropological perspective and ability to explain complex situations in a balanced manner; no one is unquestionably a saint or a sinner in his accounts.
Cowell was the antithesis of a self-publicist; at times he was abstemious, quietly self indulgent at others, able to withstand the harshness of the jungle and remarkably self-effacing. His candour, charm, gentle humour and knife-edged perspicacity endeared him to all types of people, made them listen to what he had to say and follow. He liked a glass of whisky and a good story. He felt uncomfortable with formality; he never liked to wear a tie, but sometimes he took one along ‘just in case’. He died unexpectedly of heart failure in London.