“Most art is unadmittedly competitive; graffiti is nakedly so. Writers vie for prominence of their works, their size, complexity, technique and above all their ubiquity. Elaborate etiquette regulates this rivalry, and competition is joined by overwriting a rival’s work. When I accompanied a TV team to watch the well-known writer, Prime, produce a work on a quasi-official site, the most interesting and shocking act was his first – taking a large roller to the painting already there, entirely blotting it out. If convention governs the terms of rivalry and respect between writers, it also quite rigidly governs the look of graffiti.”