"I'm currently working on a Guardian project about photography, and one of the photographers I had to write about this week was Henri Cartier-Bresson. Looking over the images that this co-founder of Magnum and master of the passing moment had produced in his long lifetime, I found myself thinking two things. First, that he was one of the great modern French artists, whose photographs you can set alongside thepaintings of Pissarro. And second, I remember the day I talked to him on the bus, in Hackney.Well, he wasn't actually on the bus with me. I was interviewing him for a feature and had given him my mobile number. So one of the great artists of the 20th century phoned me when I happened to be on the 55 bus rumbling along Mare Street in east London.Cartier-Bresson wanted to talk because he was outraged that theheirs of Picasso were giving permission to put the master's name on a car. APicasso car was an obscenity, thought Cartier-Bresson, a commercial mockery of art. So he told me as I frantically took notes.He also sent a fax, stating his anger in his own handwriting. On it was his address – he lived on the Rue de Rivoli, next door to the Louvre. Not quite Mare Street after all.Now, looking at this great artist's photographs, I feel a thrill to have chatted with a genius on the bus. As time goes by, art finds its place. Cartier-Bresson's has found a lofty level; he absolutely had the right to speak out on behalf of Picasso, in whose company he belongs."