[citation needed] He became a fellow at Trinity College in 1864, and became Assistant Tutor in 1866, Praelector in Ancient Philosophy in 1875 and Vice-Master in 1914.

In 1875, he married Margaret, daughter of the Reverend Francis Vansittart Thornton, vicar of South-Hill with Callington, Cornwall.

Together with Henry Sidgwick and others he essentially established Cambridge University's supervisory system by introducing it to the classical side at Trinity.

He became Regius professor of Greek at Cambridge University, a post he was appointed to in 1906, following Sir Richard Jebb; after 1879 he became one of the editors of the Journal of Philology until his death.

In July 1919, Jackson was honoured on the occasion of his eightieth birthday and his retirement as Vice-Master of Trinity College, with an address presented by the Master and Fellows.

Jackson's area of study was Greek philosophy, but he did not publish greatly – editing book 5 of the Nicomachean Ethics and writing a series of pieces on Plato's later theory of ideas in the Journal of Philology.

McTaggart, Frederic William Maitland (who had himself been an Apostle for twenty-five years: 1873), Nathaniel Wedd, Bertrand Russell, Robin John Grote Mayor, G.E.

Henry Jackson, who succeeded Richard Jebb as professor of Greek at Cambridge in 1906, belonged to the Ad Eundem club.

In 1913 he responded to a comment from a friend that Gilbert Murray was a "very attractive person" by saying that "Oxford is very successful in breeding 'attractive' scholars: more so than Cambridge.