Dr Mike Osborne's interest in fortifications began with childhood visits to castles and forts. It has developed over the years to include all aspects of the subject from Iron Age hillforts to Cold War bunkers. He was a volunteer-coordinator for the 'Defence of Britain Project', recording twentieth-century military structures. After a thirty-year career in education he took early retirement to write, producing twenty-six books to date on topics ranging from Civil War sieges and fortifications to the Volunteer Training Corps. His best- selling 'Defending Britain' led to a series of county surveys of defences including five titles for Fonthill and the award-winning 'Defending Cambridgeshire'.