He was the elder child of Reginald Frederick Cowling (1901–1962) and his wife, May, née Roberts.
In 1937 Cowling won a place at Battersea grammar school in Abbotswood Road Streatham, being evacuated with it following the outbreak of the Second World War to Worthing and then Hertford. In August 1943 he gained a major scholarship to read history at Jesus College, Cambridge.
After graduation Cowling registered to write a PhD thesis on the policy and politics of British India from 1860 to 1890, and spent time in 1950–51 studying in Delhi, Calcutta, and Bombay.
He produced a number of books on British history that set out to challenge some widely held assumptions about how politicians behaved—that is, that they responded straightforwardly to either electoral opinion or rational principles. 1867: Disraeli, Gladstone and Revolution(1967) was followed by The Impact of Labour, 1920–1924(1971) and The Impact of Hitler, 1933–1940(1975).
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