The interaction between context and process is a key theme in this book. Earlier chapters have demonstrated the way in which the context of world and European politics helped shape the foundation treaties of the Community. The institutions, created by those treaties, lay at the very heart of the Community. The process of integration, very much a function of institutional structure, would profoundly affect and change the entire context of European politics. It is impossible to understand the evolution of the Community and indeed of the whole course of European politics from the 1950s without reference to that institutional structure. This justifies breaking the broadly historic narrative at this point to focus on that structure. It was created by the foundation treat ies of the three legally separate communities and the slightly later treaty merging their institutions. Acceptance of, and participation in, that institutional structure was an absolute prior condition for new mem bers. As they joined - Britain, Denmark and Ireland in 1973; Greece in 1982; Portugal and Spain in 1985; Austria, Finland and Sweden in 1995 - mechanisms concerned with weighting and voting were adjusted. The structure itself was not changed as a result of enlargement, although there were over the years a series of actual amendments to enlarge the powers of the European Parliament. Even so, it is true to say that the basic institutional framework was largely unaltered for more than three decades. Not until the Single European Act, the Treaty of Maastricht on European Union and the later Treaties of Amsterdam and Nice were there any general reforms. The European Union of which the Com munity is legally a part - or to use the language of the Treaty of Maas tricht, a ‘pillar’ - comes much later in the narrative. In any event, it cannot be stressed too often that a decade after the signature of that treaty, the Community remains at the heart of the Union and its basic institutional structure is specific and different. The prime concern in this chapter is with the institutions of the European Community.