Born in Glasgow, Dewar studied History, and later Law, at the University of Glasgow. Before entering politics, he worked as a Solicitor in Glasgow. At the age of 28, he was elected to British House of Commons, representing Aberdeen South from 1966 to 1970. After losing his seat, he returned to law and even hosted his own Friday evening talk show on Radio Clyde. Dewar was re-elected in the 1978 Glasgow Garscadden by-election and served as the MP until his death in 2000. Following Labour's landslide victory in 1997, he was appointed Secretary of State for Scotland by Prime Minister Tony Blair. As the Scottish secretary, he was an advocate of Scottish devolution, and campaigned in-favour for a Scottish Parliament in the 1997 Scottish devolution referendum. After a successful campaign, Dewar worked on creating the Scotland Act 1998.