Under the influence of Lionel Curtis, Beit lecturer in colonial history 1912–1913, Coupland joined the Round Table movement, and succeeded Curtis as Beit lecturer. He became Beit Professor in 1920, succeeding Hugh Edward Egerton, despite a lack of finished work in print.[1] The choice is accounted for by the electors' wish to have a "first-class mind" rather than a scholarly specialist.[3]
With Curtis, Coupland tried to set up an African institution in Rhodes House in the early 1930s; but they were unsuccessful in obtaining funding.[4] From 1938 to 1943 Coupland assisted Lord Lugard and Hanns Vischer with the running of the International African Institute.[5] From 1939 to 1950 he was a fellow of Nuffield College, Oxford.
According to historian Caroline Elkins, Coupland's work on British imperial history had a Whig narrative of progress.[8] Coupland defended British Empire in India, arguing that there had been "no indubitably black years in the long record of the British connection with India".[9]
Coupland wrote about abolitionism in his books Wilberforce and The British Anti-slavery Movement. Trinidadian historian and politician Eric Williams objected to Coupland's account of the Slavery Abolition Act 1833, which Williams perceived as being covertly supportive of continued British colonial rule in the West Indies.[10] Coupland was one of the examiners of the 1938 Oxford D.Phil. dissertation by Williams written under Victor Harlow, on a topic suggested by C. L. R. James. It was "deferential" in comparison with the 1944 published version, the book Capitalism and Slavery, which relied on economic reasoning going back to Lowell Joseph Ragatz, to whom it was dedicated.[11][12][13] Williams made a number of points directly criticising Coupland in Capitalism and Slavery, including:
From the "Conclusion": "But historians, writing a hundred years after, have no excuse for continuing to wrap the real interests in confusion." Footnoted as: "Of this deplorable tendency Professor Coupland of Oxford University is a notable example."[14]
"Professor Coupland contends that behind the legal judgement lay the moral judgement, and that the Somersett case was the beginning of the end of slavery throughout the British Empire. This is merely poetic sentimentality translated into modern history."[15]
The Oxford History of the British Empire considers that Coupland had a "distinguished career", but that the attack by Williams "clouded" its later part.[3]