Over the past three decades, the financial system has been going through a historical phase of major structural change. This paper traces the implications of this financial revolution for the dynamics of financial distress and for policy. It argues that, despite this revolution, some fundamental characteristics of the financial system have not changed and that these hold the key to the dynamics of financial instability. These characteristics relate to imperfect information in financial contracts, to risk perceptions and incentives, and to powerful feedback mechanisms operating both within the financial system and between that system and the macro-economy. As a result, the primary cause of financial instability has always been, and will continue to be, overextension in risk-taking and balance-sheets. The challenge is to design a policy response that is firmly anchored to the more enduring features of financial instability while at the same time tailoring it to the evolving financial system. Using an analogy with road safety, policy has so far largely focused quite effectively on improving the state of the roads and on introducing buffers. More attention, however, could usefully be devoted to the design and implementation of speed limit.