Finance during the First World War might seem an arid topic, but in fact it mainlines us deep into Britain’s twentieth-century history, on at least four different levels. Firstly, and most obviously, it helps us understand the character and conduct of the war itself. Since at least the time of Thucydides, war has been ‘a matter not so much of arms as of money’, and grasping how efforts – successful or not – were made to obtain that money has been crucial to understanding any conflict.1 Secondly, by analysing the enthusiasm with which the public accepted an increased tax burden, and subscribed to war loans, we can perhaps explore levels of popular support for the war.