In 1937, during the Spanish Civil War, he left for Barcelona where he worked for SIM (Servicio de Información Militar), an intelligence service run by the Soviet NKVD.
In World War II, he was active in the French resistance, was arrested by the Nazis and sent to the Mauthausen concentration camp.
After the war, he lived in Switzerland but soon moved with family to Prague, where he became a leading figure in the Communist Party of Czechoslovakia and was eventually nominated deputy minister of foreign affairs in 1948.
After the Slánský trial, London collaborated with the authorities and served as a lead witness in other construed political processes against top Czechoslovak communists, such as Eduard Goldstücker, Josef Pavel, Osvald Závodský, Gustáv Husák, Otakar Hromádko and others.
Chris Marker made the short film On vous parle de Prague: Le deuxième procès d'Artur London, an on-set documentary about the making of this movie.