He began his photography career in 1975 working on an Italian cruise liner in the Caribbean before joining the Sygma news agency in Paris in 1976.[3] In the 1970s, Marlow worked in Northern Ireland, Angola, The Philippines and Lebanon primarily as a war photographer, but soon found that the competition of photojournalism did not suit him.
I did get some very good pictures, and was doing a lot of conflict work, but I just realised I was never ever going to be Don McCullin. And actually, in certain situations, I was very, very scared.[4]
He returned home to Britain, and worked in Liverpool on an eight-year project, Liverpool – Looking out to Sea, which documented what he perceived to be decline of the city under Margaret Thatcher.[4]
He became associated with Magnum Photos in 1980 and became a full member in 1986, having been attracted to the freedom the agency gives its photographers to work on personal projects.[4][1][5] Alongside Chris Steele-Perkins, he founded Magnum's London office in 1987.[1] He served as the agency's president twice and was vice-president numerous times.[1] The photographer Martin Parr said it was "difficult to overestimate" Marlow's contribution to Magnum".[1]
He also worked regularly for The Sunday Times in the mid-1980s.[1] In 1991 he received an assignment from the Somme department in France to photograph Amiens.[6] Later he began to work abroad again, travelling to Japan, the United States, and other parts of Europe.[7] His later photography is primarily in color.[8] Though well known for his depictions of places, Marlow also documented politics with a collaboration with Tony Blair.[3]
Marlow is also known for his photos of his three sons and wife.[2]
Marlow died on 21 February 2016 from influenza contracted during a stem cell transplant as a treatment for multiple myeloma.[9][10]
Département Somme: regards de photographes. Amiens: Trois Cailloux, 1992. ISBN2903082669. Photographs by Marlow, Harry Gruyaert, Jeanloup Sieff, Michel Vanden Eeckhoudt, Martine Voyeux and Hugues de Wurstemberger; prefaces by Christian Caujolle and Jacques Darras.
Way to Gods: Magunamu Foto: Kumano kodō, Santiago e no michi (WAY to GODS マグナム フォト 熊野古道 サンティアゴへの道), ed. Nagasaka Yoshimitsu (永坂嘉光). Tokyo: Kawade Kobō Shinsha, 1999. ISBN4-309-90293-6. (Additional title on front cover: Ancient Kumano Roads and Roads to Santiago.) Contains photographs by Marlow of Kumano kodō and camino de Santiago; as well as photographs by Elliott Erwitt, Chris Steele-Perkins and Harry Gruyaert.