Between 1928 and 1931 Catlin was attached to the personal staff of Sir Oswald Mosley. This was a period before Mosley had made his final break with the Labour Party to become openly fascist. In 1929 he assisted H.G. Wells, Arnold Bennett, and others in establishing The Realist magazine. Catlin was an unsuccessful Labour candidate in two general elections: 1931 in Brentford and Chiswick, and 1935 in Sunderland. From 1935 to 1937 he served on the executive committee of the Fabian Society. During the 1930s Catlin travelled extensively. He visited Germany, where in 1933 he witnessed the trial of Dimitrov for allegedly setting the Reichstag fire, a forewarning of what Nazism was to become. He went to Soviet Russia for a prolonged examination of the newly established Communist regime there and to Spain during the height of the Civil War. During this period Catlin wrote a large number of articles as a journalist, mostly for the Yorkshire Post. He served on the campaign team of Presidential candidate Wendell Willkie during 1940 and his subsequent book, One Anglo-American Nation appeared in 1941. He was an early advocate for the independence of India, after meeting Mahatma Gandhi in 1931 in London. He visited India in 1946 and 1947 and published a tribute to Gandhi after his assassination, In the Path of Mahatma Gandhi (1948). In 1947 Catlin lectured in Peking. He served as Provost of Mar Ivanios College in India for 1953–54 and as chairman and Bronfman Professor in the Department of Economics and Political Science at McGill University between 1956 and 1960. He was a founder of the Movement for Atlantic Union, which was established in 1958. He drafted the constitution of the Paris-based Atlantic Institute, founded in 1961. He was also a member of the Pilgrims Club of Great Britain. His autobiography, on which he had worked sporadically since the end of the First World War, was finally published in 1972 as For God's Sake, Go. Honours In the 1970 Birthday Honours, Catlin was knighted for services to Anglo-American relations. Private life Catlin married the English novelist Vera Brittain in 1925 after a courtship that began as a correspondence. She was pursuing her own career as a writer in Britain and the marriage endured many Atlantic-wide separations. They had two children: John Edward Jocelyn Brittain-Catlin (1927–1987), whose memoirs, Family Quartet, appeared in 1987; and the Liberal Democrat politician Shirley Williams,