He served in World War I with the York Rifles and Machine Gun Corps, becoming a major.
In 1927, he became a fellow of Gonville and Caius College, Cambridge, then in 1930, he transferred to the University of Liverpool, where he held the Brunner Chair of Economic Science.
[1][2] Bellerby was a supporter of the Labour Party, and stood unsuccessfully for the party in Newark at the 1931 United Kingdom general election, and Cambridgeshire at the 1935 United Kingdom general election.
[1][2] After a period out of academia, Bellerby became a Leverhulme Research Fellow in 1940, then a lecturer at the University of Glasgow in 1942, but spent the remainder of the war working for the Ministry of Food.
From 1947, he worked at the Oxford Institute of Agricultural Economics Research, retiring in 1961, though he was a director of Hunter and Smallpage for a few years later in the decade.