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)

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

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

Churchill (London: Quercus, 2011)

US edition (2014); Slovene edition (forthcoming)

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)

Buildings of Empire (Oxford University Press, 2013)

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

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

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

Arabic edition (forthcoming)

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

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