Born in Dublin, Megaw was the son of Irish politician and judge Robert Megaw and the brother of the crystallographer Helen Megaw. After the creation of the Irish Free State, his father, a strong Protestant, relocated the family to Belfast. He was educated at the Royal Academical School in Belfast, before being elected to an open scholarship in Classics at St John's College, Cambridge. After gaining a first in Part I of the classical tripos, he switched to Law, gaining a first in Part II of the law tripos and in the LLB. He then attended Harvard Law School on a Choate fellowship. He also played rugby union internationally for Ireland, delaying his called to the bar for a term to take part in a match. Megaw was called to the bar by Gray's Inn in 1934, having gained a certificate of honour in the bar finals. He became a pupil of Henry Willink at 3 Essex Court, and became a tenant there. Through devilling for Willink, Megaw became known to the India Office, and was regularly retained by the Indian government to appear in front of the Judicial Committee of the Privy Council. His practice was mainly in commercial law, in which he distinguished himself. Megaw married in 1938. The same year, disapproving of the Munich Agreement, he joined the Territorial Army. Called up as a gunner in 1939, he saw active service in London during the Blitz, before being posted to a staff position in Washington DC. He was demobilized with the rank of colonel and was awarded the US Legion of Merit. Returning to the bar after the war, Megaw took silk in 1953, and was made silk in Northern Ireland, even though he did not practice there. He was appointed Recorder of Middlesbrough in 1957 and elected a bencher of Gray's Inn in 1958, serving as treasurer in 1976. During his career at the bar he acted as pupilmaster to Michael Kerr and was a chambers contemporary of John Donaldson.
Judicial career
In 1961, on the recommendation of Lord Kilmuir, he was appointed to the High Court, receiving the customary knighthood. Assigned to the Queen's Bench Division, he also became President of the Restrictive Practices Court, but resigned from the latter in 1968, in protest against the government's use of legislation to overrule the court. In December 1964, he sentenced Ronald Cooper to death for murder, becoming the last judge to pronounce a death sentence at the Old Bailey. He was promoted a Lord Justice of Appeal in 1969, and was sworn of the Privy Council. Having become dissatisfied with judicial work and aware that he would not be promoted to the House of Lords, he retired during the Long Vacation with little fanfare. After his retirement, he occasionally sat on the Privy Council and as an arbitrator. In 1981–82, he chaired the Committee of Inquiry into Civil Service Pay, formed in the aftermath of a Civil Service strike.
John Megaw was also capped twice as an international rugby union player for Ireland in the 1930s, once 1934 against Wales and again in 1938 against England, both times playing at Number Eight. Ireland lost both tests.
