Innocently cycling along the canal towpath in Little Venice, west London, I am witness to an unfortunate accident. Another cyclist veers in such a way that a third has no choice but to take a dive into the uninviting waterway. I assist the poor fellow out of the water and onto the towpath. Thinking he might want further assistance I offer him my card. He studies it intently, then says (with a dignity and grandeur which causes me to forget his water-soaked appearance): 'I am David Chipperfield'. I genuflect and move on . . .