The city compelled the imagination in all kinds of ways. Its greatest fascination, though, was undoubtedly its greatest monstrosity - the Wall, the hideous concrete barrier, enforced by armed guards and a complex series of lethal mantraps, that the East German government had been forced to erect in 1961 to stop the massive haemorrhage of its citizens to the West. Another much longer wall, from the Baltic to Thuringia, divided the German Democratic Republic from West Germany proper, but the Berlin Wall obtruded more on the consciousness because it closed in the Western half of the city as tightly as the fence round a suburban garden. Wherever you went you came face to face with it barring the street you were in, and defining the geography of Berlin even more sharply than the Hudson river does the geography of New York.

Somewhere out of sight behind it that summer Egon Bahr and Michael Kohl, the representatives of the Federal and Democratic German Republics respectively, were negotiating the terms of the Basic Treaty by which the West was at last to recognise the East, and by which relations between the two states were at last to be given some semblance of normality. Already a new agreement on Berlin itself, signed by the four former allies, was for the first time making it possible for West Berliners to visit the Eastern half of their city. Friends of mine came back to the modern wonderland of West Berlin stunned by the different kind of wonderland that they had found on the other side of the Wall: cobbled streets, unlit villages, pockmarked tenements, snorting steam trains — the long-lost old Germany of the Weimar Republic and the Third Reich, magically preserved in all its nostalgic dullness and shabbiness, as if in some vast grey heritage park, by the conservatism of the Communists and the backwardness of their economy.

The existence of this other Germany, and the endless puzzle of its relations with the Federal Republic, was part of what made modern German politics the most interesting in Europe. How even to refer to it officially without seeming to acknowledge that it was a separate state? The right-wing press stuck with 'the Soviet Zone', or even simply 'the Zone', long after it had acquired a government of its own. The usual official euphemism was 'the other part of Germany'. Kiesinger, Brandt's predecessor as Chancellor, described it not as a state but a 'phenomenon'. Brandt was prepared to concede that it was a state, but refused to see it as a foreign one. As he famously said, in the statement of his new government's policies in 1969: 'Even if two states exist in Germany they are not foreign to each other; their relations to each other can only be of a special sort.'