Affectionately known as Croicks, Ste Croix taught part-time at Birkbeck from 1950 to 1953, before moving to New College Oxford. He was a member of the Communist Party of Great Britain and was to remain a committed Marxist and atheist all his life.

During his time at Birkbeck, Ste Croix composed one of his classic articles, “The Character of the Athenian Empire” (1954), which was to dwell on themes that continued throughout his career, including slavery, persecution, democracy, the poor, and the baneful impact of Christianity.

In the article, he contrasts two very different meanings of the Greek word δημοκρατία. According to one meaning, the whole people are sovereign; in the other, sovereignty resided with the mass of poor people. The government by all citizens was the definition employed by democrats. Government by the poor was the way oligarchs defined it, in Marxist terms, the “dictatorship of the proletariat”.

He was, according to his own reckoning, “politely militant”.