Then he pushed on south to Cheapside, where the farmyard bleats were drowned out by the clank of metal on anvil and the pounding of nails into wood or leather, as the blacksmiths, goldsmiths, silversmiths, tanners, dyers and potters all laboured, and the cowshed stink was replaced by the stench of the fullers’ urine jars. Cheapside was a magnificent, unending festival of trade. You could buy anything you wanted here, from a hot veal pie to a flagon of beer, from a Flemish-style hat to Italian-style shoes, from imports like French linen and Spanish silk to eastern spices and Scandinavian walrus ivory - from the words of an apocalyptic preacher that would fire your soul, to the moist quim of a girl to soothe your body. For Harry this was a wonderful place to be, for all the stinks and the filth and the crowding, and the beggars that swarmed like crows pleading for spare farthings.

Harry was Oxford born and bred, but he was a merchant, and England’s capital of business felt like a second home to him. And in Cheapside industry and commerce pulsed as nowhere else in England.

But today Harry was not here for trade.

He pushed further south still, past the walls of Saint Paul’s, and through narrowing streets lined with warehouses. Their walls were plastered with posters bearing apocalyptic pronouncements from the Bible. He looked at the posters curiously, for they were printed, a novelty still rare in Oxford.

He came at last to the river bank. He could just make out the brown, filthy water through a forest of cranes and ships’ masts and furled sails, and he could hear the cursing of the stevedores in a dozen languages. He was near the old bridge, the only span over the river to the south bank. To his left there was the ugly pile of the Tower, to his right the great palace of Westminster with the abbey beyond, in their suburb around the bend of the river. He turned right and walked perhaps a quarter of a mile along the bank. When he came to the ancient dock road called the Strand he cut north, heading inland past more warehouses and factories.

And here he found, just where the monk’s letter had described, a small, gloomy parish church, its roughly cut stone stained black by city soot. Chantries clustered around the church, chapels devoted to the souls of the long-dead rich. A stone tablet told him that the church was dedicated to Saint Agnes, a virginal martyr of Rome, and his sister’s patron saint.

He felt a deep reluctance to enter. But it was to here that he had been summoned.