Soon after his birth John and Hilda Shawcross brought their son back to England. Shawcross took an early interest in politics and by the age of 16 he had joined the Labour Party and was ward secretary in Wandsworth. He was also involved in the party's campaign during the 1918 General Election.
A brilliant student, Shawcross decided to study French in Switzerland. While there he became translator to the British delegation at the Socialist International held in Geneva. He met Ramsay MacDonald and Herbert Morrison, who suggested that Shawcross should become a lawyer.
After obtaining a first class honours degree in law he moved to Liverpool. As well as working as a lawyer in the city he also lectured at the University of Liverpool (1927-34). Despite his left-wing views he was willing to work for the coal-owners during the court-case that followed the 1934 Gresford Colliery Disaster. Richard Stafford Cripps represented the miners.
During the Second World War Shawcross chaired the Enemy Aliens Tribunal (1939-41) and Deputy Regional Commissioner for the South-East (1941-42) and Commissioner for the North-West (1942-45).
In the 1945 General Election Shawcross won with a large majority at St. Helens. The new prime minister, Clement Attlee, immediately appointed Shawcross as Britain's Attorney General. In this role he led the British prosecution at Nuremberg.
Shawcross also prosecuted William Joyce for high treason in September, 1945. In court it was stated that although he was United States citizen he had held a British passport during the early stages of the war. It was therefore argued in court by Shawcross that Joyce had committed treason by broadcasting for Nazi Germany between September 1939 and July 1940, when he officially became a German citizen. Joyce was found guilty of treason and was executed on 3rd January 1946.
In the House of Commons Shawcross promoted the Trade Disputes and Trade Unions Bill, redressing anti-union legislation (the 1927 Trade Disputes and Trade Union Act) that was passed by a Conservative government following the 1926 General Strike. During the debate on this legislation Shawcross remarked: "We are the masters at the moment, and not only at the moment but for a very long time." He was much attacked for this and later he admitted it "was the most stupid thing I ever said."
In April 1951 Shawcross was appointed President of the Board of Trade. However, he lost office when the Labour Party lost the 1951 General Election. After this he concentrated on his lucrative law career and eventually retired from the House of Commons in 1958. When he became a life peer later that year he sat on the crossbenches of the House of Lords, although in the 1980s he supported the Social Democratic Party.
In later life Shawcross sat on the boards of a wide variety of different companies including Hawker Siddeley, Shell, EMI, Rank-Hovis-McDougall, Times Newspapers, Dominion Continental Bankers and Thames Television.
Hartley Shawcross, Lord Shawcross of Friston, died on 10th July, 2003.