The London Apothecaries Hall

London, like all great cities, lives on and amongst its past. Its urban form is created by the rival pressures of dynamic change, on the one hand, and the forces of preservation on the other. As a result, the old and new everywhere mingle. Old field patterns lie under modern estates. Old buildings sit shoulder to shoulder with new. The past lies round every corner.

All this keeps the historian busy, as he or she walks around town – in the recommended style, with eyes open, senses alert, and notepad at the ready. Postmodernists may sweepingly claim, with Jacques Derrida, that 'there is nothing outside the text'. But for urban historians the visible city is itself a prime source of study. Its built environment carries its own messages, that are complemented and enhanced hut not replaced by the documentary record.