Londonist again. For you who enjoy gleaning a sense of what came before in places you visit, have a look at Londonist's Anglo Saxon map of London. In their words, "a map showing the London area in Anglo Saxon times (roughly speaking, 500-1066AD). It’s pieced together from many resources, showing our guess at the roads, rivers, forests and marshland that characterised the region. The main purpose was to highlight the many villages, hamlets and farmsteads whose names are still part of modern London."
And don't neglect links on the page for more fascinating possibilities, such as London's vanished castles and the ever-popular mystery of Oyster zone boundaries.