Alan graduated with a degree in Politics and Philosophy from Southampton University and went on to achieve a Ph.D. in Political Science. In 1980 he became a city councillor and then Leader of the Council when Labour took control in 1984.

He worked in research for two national charities during the 1980s and early 90s, and in 1992, came off the City Council and became Professor of Public Policy at Southampton Institute (now Southampton Solent University).

Alan was nominated by the Labour Party to stand for the swing seat of Southampton Test in the early 1980s. He made solid progress in the seat in 1987 and 1992, and finally won in 1997. Alan was re-elected as the Labour MP for Southampton Test in 2015 with an increased majority. This was only the third time in the constituency's history where it bucked the national trend by electing an MP from a different party to the one that would go on to form a government. Alan was re-elected with an increased majority in 2017.

In December 1999, he was appointed as Parliamentary Private Secretary to Baroness Blackstone, Minister for Higher and Post-16 Education. From June 2001 - May 2002 he served as Minister in the Department for Transport, Local Government and the Regions, responsible for Local Government, the Regions and the Fire Service.

His special interests now include further and higher education, local government, constitutional affairs, the environment, energy and transport policy.

Alan has been the Shadow Energy and Climate Change Minister since October 2016 and served as the Shadow DECC Minister for Generation and Transmission September 2015 – June 2016. Prior to this, Alan was the Chair of PRASEG, the Associate Parliamentary Renewable and Sustainable Energy Group and Co-Chair of APSRG, the Associate Parliamentary Sustainable Resource Group. His special interests include further and higher education, local government, constitutional affairs, the environment, energy and transport policy.

He is a Fellow of the Institute of Waste Management, and member of the Board for The Environment Centre (Southampton) and the Centre for the Third Age (Southampton). He is a Visiting Professor in the Faculty of Media, Arts and Society at Southampton Solent University.