Botswana 1939-1945: An African Country at War (Oxford University Press, 1999)

War and Empire in Mauritius and the Indian Ocean (Macmillan, 2001)

The British Empire and the Second World War (Hambledon Continuum, 2006); hardback and paperback

Mad Dogs and Englishmen: A Grand Tour of the British Empire at its Height, 1850-1945 (Quercus, 2009); hardback and Kindle version

Distant Drums: The Role of Colonies in British Imperial Warfare (Sussex Academic Press, 2010); hardback and paperback

Churchill (London: Quercus, 2011); hardback and paperback; US edition (2014); Slovenian language edition (2018)

Illustrating Empire: A Visual History of British Imperialism with David Tomkins (Oxford University/Bodleian Library, 2011)

The British Empire: A Very Short Introduction (Oxford University Press, 2013); German edition (2015); Chinese edition (forthcoming); Kindle version

Buildings of Empire (Oxford University Press, 2013)

The British Empire and the First World War, edited (Routledge, 2015); hardback and paperback

 An Imperial World at War: The British Empire, 1939-1945, edited with Yasmin Khan and Gajendra Singh (Routledge, 2016); hardback and paperback

Persian Gulf Command: A History of the Second World War in Iran and Iraq (Yale University Press, 2018); audiobook version (2018)

Ceylon at War, 1939-1945 (Helion, 2018)

Of Islands, Ports, and Sea Lanes: The Second World War in Africa and the Indian Ocean (Helion, 2018)