A lifelong and keen aircraft spotter, Derek was a sparetime volunteer member of the Royal Observer Corps for nearly fifty years and wrote the history of the Corps in his 1975 book "Attack Warning Red : The Royal Observer Corps and the Defence of Britain, 1925 to 1975", later updated in 1992 when the Corps was stood down. Derek joined the Royal Observer Corps in 1947 and served on posts near Chichester, London, and at Cuckfield (north of Brighton) after moving there in the 1960s. As a journalist and aerospace expert he did his utmost to further the Corps' standing in both military and civil areas.