The friction broke out as a riot in 1327 after which the strong stone screens and doors which wall off the eastern end of the church from the nave were built. The priory itself was walled off from the town at this period. An oratory was established "in angulo navis" ("in the corner of the nave") for the reserved sacrament; it is not clear which corner was being referred to, but Dr Palmer argues that the buttress against the north-west tower pier is the most likely setting. He notes the arch filled in with rubble on the aisle side; and on nave side there is a scar line with lower quality stonework below. The buttress is about thick, enough for an oratory. Palmer notes that provision for reservation of consecrated hosts was often made to the north of the altar which would be the case here. The central tower was at last raised by Hamo de Hythe in 1343, thus essentially completing the cathedral. Bells were placed in the central tower (see Bells section below). The chapter room doorway was constructed at around this time. The Black Death struck England in 1347–49. From then on there were probably considerably more than twenty monks in the priory. The modern paintwork of the quire walls is modelled on artwork from the Middle Ages. Gilbert Scott found remains of painting behind the wooden stalls during his restoration work in the 1870s. The painting is therefore part original and part authentic. The alternate lions and fleurs-de-lis reflect Edward III's victories, and assumed sovereignty over the French. In 1356 the Black Prince had defeated John II of France at Poitiers and taken him prisoner. On 2 July 1360 John passed through Rochester on his way home and made an offering of 60 crowns (£15) at the Church of St Andrew. The Oratory provided for the citizens of Rochester did not settle the differences between the monks and the city. The eventual solution was the construction of St Nicholas' Church by the north side of the cathedral. A doorway was knocked through the western end of the north aisle (since walled up) to allow processions to pass along the north aisle of the cathedral before leaving by the west door. In the mid-15th century the clerestory and vaulting of the north quire aisle was completed and new Perpendicular Period windows inserted into the nave aisles. Possible preparatory work for this is indicated in 1410–11 by the Bridge Wardens of Rochester who recorded a gift of lead from the Lord Prior.