Because medieval London, the London of knights and sieges and plague and enormous political drama, is not gone. It is not buried under glass offices and coffee shops, lost entirely to the Great Fire of 1666 and the Blitz and two thousand years of continuous rebuilding. It is hiding in plain sight. In churches, in ruins, in underground rooms, in a meadow beside the Thames, in two giant wooden statues paraded through the City every November.

1066 was a rather big year for castles in England. Before this date there were four, maybe five, castles found in the whole country. By 1100, just thirty-four years later, there were over five hundred!