War is an expensive business. By the end of the Nine Years’ War (1688-1697), England’s national debt amounted to around 20 percent of national income—a low figure by today’s standards but a worryingly high one to contemporaries. But as anyone who has ever had a mortgage or any other sort of loan knows, what matters is not just the quantum of the borrowing but its costs. As England (and, after 1707’s Act of Union with Scotland, Great Britain) established that it would not miss a payment and as