Presenter Richard Taylor explains how churches were originally simple buildings intended to protect the altar and the most important Christian rite of all, the Eucharist. He visits Britain's finest early medieval churches to untangle the mystery of why the Anglo-Saxons and Normans seem to have been unwilling to shake off their pre-Christian past and to have continued to fill their sacred buildings with mysterious pagan images. An ancient book in an Oxford library helps Richard find an answer.