[2] A Cambridge Apostle, he was called to the Bar at Lincoln's Inn in 1894, becoming a Bencher in 1915 and King's Counsel (KC) in 1919.

He was Recorder of Colchester from 1924 to 1928,[4] and a Judge of the High Court of Justice, King's Bench Division from 1928 to 1947.

[5] Knighted (KBE) in the 1920 New Year Honours for services during World War I as Director of the Foreign Claims Office[6] and appointed a Privy Counsellor in the 1948 New Year Honours,[7] Macnaghten was Commissary of the University of Cambridge from 1926.

He married Antonia the eldest daughter of social reformer Charles Booth and had three daughters, all of whom became socialists and married communists including the artist Peter Laszlo Peri, and one son.

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