Everyone thinks they know London. Its landmarks have been used in a hundred films, its skyline and riverscape instantly recognizable. For London has been at the centre of the nation’s and even the world’s attention, on and off, for two thousand years. Yet familiarity does not necessarily bring enlightenment. The very size and bedeviling complexity of the city have the power to obscure and to mesmerize; the unparalleled tangle of experience over such a long period of time can seem impossible to unravel. What, then, was London? It was a capital city, a major port, an economic powerhouse, a magnet for talent and ambition. It was wealthy, populous, central to the nation, cosmopolitan yet self-absorbed and inward-looking. People have always migrated to London, from elsewhere in Britain as well as overseas, either to work or to seek a better life.