blocked. Above this is a rib vault decorated with twelve carved bosses. Over the west arch is a three-light Perpendicular window. In the top stage are three-light louvred bell openings on each side. The parapet is crenellated, with corner pinnacles and statues. Along the south wall of the south aisle are five buttresses, with three three-light windows in the eastern bays. The western bay incorporates a two-storey porch. Under the easternmost window is a priest's door. Also on the south wall is a sundial dating from the 17th or 18th century. Along the clerestory are eight three-light Perpendicular windows. At the east end of the chancel is a large five-light window with Decorated tracery, and at the east end of each aisle is a three-light window. The north porch also has two storeys. The arch over its doorway is decorated with a band of shields, and over the arch is a niche for a statue and a three-light square-headed window. Interior At the east end of the church the altar is surrounded by a massive wooden surround, known as a baldachin. It is thought that this had been made for the church of St Miles Coslany in 1741 and moved into St John's in 1917. Behind the altar is a painting of the Last Supper attributed to the Renaissance painter Livio Agresti. There is another altar in the north aisle. The font dates from 1864, and is decorated with inlaid pieces of coloured marble. The pulpit dates from the same year. Above it is a sounding board from the 17th century. The revolving lectern dates from the 18th century, and is probably Italian. Around the church are memorials to local historical personages, including Thomas Rawlins, Joseph Stannard a Norwich School painter of marine-scenes, Walter Nugent Monck founder of the Maddermarket Theatre and Margaret Howard, Duchess of Norfolk, who died in 1564. The church also houses commemorations of several mayors of the City throughout the centuries including the Southerton's, Bubbin and Ralph Segram (died 1472). Segram was a merchant who became a member of parliament and Mayor of Norwich. He commissioned a rood screen for the church, from which two panels of painted oak are now in the Victoria and Albert Museum in London. One panel depicts both William of Norwich, holding a hammer and with three nails in his head, and Agatha of Sicily, holding pincers and her severed breast.