He studied as an undergraduate at Keble College, Oxford, and subsequently at Keele University, where he was awarded a PhD in History.
His first book, based on his doctoral thesis, concerned the history of post Irish Civil War Republican politics and was titled Radicals and the Republic, Socialist Republicanism in the Irish Free State (1994).
This book, predominantly a history of the modern Provisional IRA, won the politics book of the year award from the Political Studies Association and was shortlisted for the Christopher Ewart-Biggs Memorial Prize.
[3] He has also co-edited two volumes: The State: Historical and Political Dimensions (1999, with Charles Townshend); and Rethinking British Decline (1999, with Michael Kenny).
In 2017, he delivered the Gifford Lectures on Nationalism, Terrorism and Religion at the University of Edinburgh.