St John's C of I Church, 161 Central Promenade, Newcastle, Ballaghbeg, County Down

St John's Church of Ireland is a gothic church built in 1832 on the west side of Central Promenade in Newcastle, situated on a slight rise. It is a significant local landmark, occupying a mature and well-established site.

The original structure was a simple gabled building with provision for a tower and spire, designed by builder and architect John Lynn and commissioned by the local landlord and patron Lord Annesley. The church was constructed at a final cost of £1,500, considerably exceeding the original estimate of £700. The nave was extended in 1876 at a cost of £1,195, the transept was added in 1902 to designs by Henry Seaver at a cost of £300, and a flat-roofed choir robing room was added to the west of the transept in 1970. The organ was installed in 1902, and the bells were replaced in 1979.

The church is built predominantly of random granite, with slightly more squared blocks used in the tower and more rounded stones in the rear walls. The spire is finished in ashlar coursing. The transept and south face of the nave are rendered with lime, though the render on the north face of the nave has largely deteriorated. Pitched roofs are finished in Bangor Blue slates.

The centrally positioned three-storey tower is surmounted by an octagonal spire topped with a ball finial. At the base of the spire are four small octagonal minarets, which surmount stepped diagonal buttresses framing the tower. The ground floor east front of the tower features a flat, almost Tudor-style pointed arch-headed doorway with double timber panel doors featuring gothic arch heads, surmounted by a fanlight also decorated with a gothic arch motif. Above the doorway is a stone panel bearing a Latin inscription recording that the church was erected by William Richard, Earl Annesley, in 1832. A carved panel above depicts the Annesley crest with two military figures—one apparently Roman and one apparently Moorish—supporting a shield surmounted by a coronet. The north face of the ground floor tower is blank, while the south face has a lean-to porch with a pointed arch doorway opening east and a small lancet window to the south. This lean-to porch now forms the main entrance to the church, with the original doors permanently closed and the steps removed. The first floor has roundels to the north, south, and east faces, the east roundel containing a traditional clock with black face, gilded hands, and Roman numerals. The second floor has tall lancet openings to all faces with louvered infills. String courses articulate the tower above the ground and first floors, with the first floor string course continuing on the church gable to suggest a pediment.

To either side of the tower, the exposed gables of the church feature tall lancet windows with small leaded panes. The south face of the nave has two tall, evenly spaced lancet windows. The projecting gabled transept projects from the left of this face, with a pointed arch doorway on its east face. The south face of the transept has three lancet windows, the centre one being slightly taller. The west face of the transept is blank. A large flat-roofed extension used as a minor hall fills the square enclosed by the sanctuary and transept, enfolding a former lean-to extension that houses the organ. The north face of the nave has three evenly spaced lancet windows. The right side of this face is overlapped by a projecting lean-to porch merging with a larger lean-to extension. The east face of the first lean-to has an arch-headed doorway. The north face has a single lancet window opening to the first lean-to, two lancet windows, and one square-headed door opening to the second lean-to, which houses the choir stalls. The chancel's west face has three lancet windows, the centre one being slightly taller. To the right is the blank side of the flat-roofed extension, and to the left is the side of the second lean-to with one almost centrally placed lancet window.

The nave, chancel, and transept roofs are gabled and finished with parapets; the chancel roof pitch is much shallower than that of the nave, and the lean-tos have even shallower pitches. Window openings are finished with stone dressings.