I have been meditating on the full impact of the William Kentridge exhibition Thick Time at the Whitechapel:  a set of six installations consisting of film, music, history, animation, humour and memory, owing as much to a sense of thoughtfulness about the nature of history as to drawing and art.   Best of all is the first grand installation, The Refusal of Time, partly because of its length and epic scale and the relationship between the machine in the middle like a printing press, and the confidence of the changing imagery on the walls around, beginning with a metronome and ending with a people’s march:-