After graduation, he took a post as a lecturer at the
University of Sheffield (1965–69), and then later at the
University of Manchester (1970–73). He became a Fellow and Tutor in Modern History at
Balliol College in 1973. In 1990, he took a post at the
University of Chicago as Professor of History, where he became chair of the History Department in 1992 and Dean of the Division of
Social Sciences in 1993. He returned to Oxford in 1994 to become Master of Balliol College (1994–2000). Lucas was the first Oxford Vice-Chancellor to serve for seven years (1997–2004), during which time he implemented many changes in the University governance structure, such as the adoption of external members to the University's Council, a radical restructuring of the committee system, division of academic departments, the establishment of a University Committee on Access and the adoption of new resource allocation and financial management systems. On his retirement as Vice-Chancellor, Lucas was appointed Warden of
Rhodes House, Oxford, responsible for the running of the
Rhodes Scholarships (2004–2009). He had previously served as a Trustee of the
Rhodes Trust. ==Personal life==