Holmes wrote more than twenty published books, including "Firing Line" and "Redcoat", and was also Editor-in-Chief of the Oxford University Press' "Companion to Military History". His television works included writing and presenting documentary series on the American Revolution such as "Rebels and Redcoats" in 2003 and "Battlefields", a series concentrating on the bloody battles of the Second World War. His "War Walks" television series has been regularly repeated on British terrestrial and digital television channels, including BBC Two and UKTV History. One of his documentary series was "Wellington: The Iron Duke", in which he chronicled the Duke of Wellington's life, travelling to India, to Waterloo and numerous other locations.