Dr Mike Osborne's interest in fortification began with childhood visits to castles and forts. It has developed over the years to include all aspects of the topic 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-five books to date. Topics include: Civil War sieges and fortifications, drill halls, the Volunteer Training Corps, the best-selling Defending Britain, and a series of county surveys of defences including four titles for Fonthill and the award-winning Defending Cambridgeshire.