Grade 1 Listed Building. Slimbridge Anglican parish church. Early 13th C - the nave and its four-bay north and south aisles were built circa 1200 - but the west tower, spire and the chancel date to the late 13th C. Clerestorey windows added in 1845 by Francis Niblett. Decorative pierced parapet to raised nave roof added at this time. The church is constructed in fine Cotswold oolite limestone, also large areas in blocks of tufa. Clerestorey walls in marlstone. Small quatrefoil window, above chancel arch, at east end of nave. Welsh slate roof to chancel Two-storey south porch; and two-storey sacristy on north side of deep chancel. Three-stage tower with pinnacles at 45 degrees; open 14th C parapet; and octagonal spire with lunettes on cardinal faces. Diagonal buttresses to tower. Stair clamp on north-east corner of tower. Gargoyles on external walls of north and south aisles. Stone sundial with ball finial on apex of porch roof. St. John the Evangelist's church is a very good example of the Early Gothic style of the 13th C.