There are two stories of the birth of the euro: an “immaculate” conception and a worldly one. The latter is, as one would expect, rather more exciting. Although the idea of a European monetary union had been floated by Eurocrats in the 1970s and ’80s, in the belief that it would hasten European economic and political integration, the key moment occurred on Dec. 8, 1989. The Berlin Wall had just collapsed. With West Germany pressing for almost immediate German reunification the traditional balance of power inside the European Community was threatened.