There are times when history produces images to equal those of the imagination, in their vividness and their consequent ability to live on in the mind. Even the rapid succession and short life of events on film and television news, which have often made them public in the first place, cannot dislodge them. Two such images stay in my head from 1989. The first, from China, is of a diminutive figure carrying a bag in each hand, facing a huge cumbersome tank, trying to sidestep it to left and right, as if it were another person encountered in a narrow passage or doorway: and not sidestepping, but outflanking it, defeating it simply by being there. For, in the face of that clanking engine of oppression, what could have been in those bags (which seemed to balance one another at the end of the carrier's arms almost like the scales of justice) but in one, hope, in the other, a soul'? In the same year, newspaper and television pictures from Romania showed jubilant crowds celebrating what appeared to be the end of a dictatorship - a moment heraldicly enacted by a round hole cut in the middle of the national flag, where the emblem of the regime had been. At the centre of those hoisted banners, a view through to blue sky, to the infinity of renewed potential.

If such moments reverberate in the imagination, in the world of historical contingencies they can sometimes appear all too fleeting, ...