The Chancellor of the Exchequer and the Treasury rose, and then rose again in its place in the twentieth, and rose again in the twenty-first century, to become, the biggest single challenge to the authority of the prime minister. No longer subordinate at all. Naked power, ambition, the knowledge that some were virtually unsackable, command over the purse and the backing of the mighty resource of the Treasury compared to the puny No. 10, ensured that Chancellors could be a power to themselves, strutting around Westminster and Whitehall at times like an overmighty baron in medieval England, making the job of prime minister at times impossible. Reaching this elevated position was not preordained, as we shall see in this chapter, and occurred through seven successive pulses, each associated with a commanding figure, usually the Chancellor, who has shaped the office, much as our landmark prime ministers have done to their own office. There are three great contemporary problems with the Treasury: its handicapping of the prime minister in shaping government strategy, its prioritising of financial over economic policy, and a diminishing role of Parliament in its oversight, have all had long roots.