Holy Trinity Church, The Diamond, Ballycastle, Co Antrim

Holy Trinity Church is a fine example of mid-18th-century church design in neoclassical style, prominently sited on The Diamond in Ballycastle's town square and conservation area. It represents the prosperity of Ballycastle during its heyday and the achievements of the Boyd family, who guided the town's development from the early 18th century.

The church was built around 1756 by Hugh Boyd, who had purchased the Ballycastle estate and village in 1727 from the Earl of Antrim on perpetual lease. The church was consecrated in 1756 at a cost of £3,000, and Hugh Boyd is buried in a crypt beneath it. Early 20th-century alterations added a vestry and raised the chancel floor. The building was externally cleaned around 1990 (with Rainey as contractor and R Robinson & Sons as architects) and underwent interior renovation around 1993 following flood damage. The church continues to suffer occasional flooding from a piped stream that runs past the site.

The building is a four-bay Georgian-style church with a western tower and octagonal spire, an eastern apse, and a slated roof. The entrance façade is dressed with ashlar sandstone. A pair of square-headed entrance doors at the base of the tower, each with three moulded panels, sits centrally within a dominant pedimented classical surround. This surround features three-quarter engaged fluted Doric columns on each side with square bases and frieze. The two-storey tower projects forward of the gabled front, breaking the pediment. A moulded stringcourse at the base of the tower carries across, defining storey heights.

On the second storey, centrally above the doorway, is a neat Venetian window composition with an arched centrepiece glazed with 37 small panes. The side panels are filled with ashlar stonework divided by plain pilasters in Doric style. Above this is a large circular clock with Roman numerals, its diameter equal to the width of the arched glazed window plus two pilasters. The second storey of the tower terminates with a cornice stringcourse surmounted by a stone balustrade, which continues around all four sides. From within the balustrading a plain octagonal spire rises, topped with a bell finial surmounted by a cross-like lightning conductor.

On each side of the principal doors are secondary entrances, similar in appearance but smaller. Each has a lugged architrave with triple keystones. Over the side doors is a moulded framed panel, and above that a rectangular window glazed in decorative glass with small square panels, framed with a moulded architrave. The overall width of window and architrave equals that of the door below. The gables on either side of the tower have thin bargestone edges, flattening out at the bottom to form kneelers. The arrises of the gable and tower feature short and long moulded quoins. Below the cornice runs a plain frieze band, continuing along the long walls under the eaves. The entire west front, tower, and spire are dressed with carefully executed ashlar sandstone.

Incised inscriptions appear on the west front. Over the central door is "Fear God, Honour the King", with the date 1756 in the tympanum. The larger panels over the side doors bear biblical verses: "Keep thy foot when thou goest to the House of God / and be more ready to hear than to give the sacrifice of fools" (Ecclesiastes 17), and "Not for asking the assembling of ourselves together" (Hebrews 10:25).

The north face of the tower, at second-storey level, has a square-headed window. The south side features no window but a sundial. The east side is blank. Some facets of the spire have circular holes, presumably for air movement rather than decoration.

The south elevation has four semicircular-headed windows with moulded architraves featuring keystones and impost blocking pieces with double cills, all trimmed in sandstone. A low simple sandstone plinth sits at ground level. A plain frieze band and projecting corbel course are located at the eaves. Cast-iron guttering is attached, with a single cast-iron downpipe painted black. The roof is slated in natural slates with plain ridge tiles. Windows are storm-glazed. Walls are smooth-rendered and lined. Moulded quoins are located at each corner.

The apsidal east end features an unusual Venetian window arrangement on the curve, comprising three round-headed lancets with the centre one higher. The curved roof is slated. There is a sandstone plinth and frieze bands, with the wall rendered smooth except for the sandstone surround to the windows.

The north elevation is similar to the south but with a small vestry projecting from the north-east corner, overlapping the nave wall as far as the first window. The vestry walls are finished in smooth rendering. Its west and north walls each have a single small round-headed two-pane double-hung sliding sash window. The vestry entrance door is six-panelled. The vestry has a hip roof with natural slates and red ridge and hip tiles. Along the vestry west wall, steps lead down to a basement heating chamber, with a decorative metal rail for protection. Projecting from the nave wall at the third window is a railed-off sealed access to the Boyd burial crypt.

The church is sited on the east side of The Diamond within a small walled and railed plot with some mature trees on the north and south sides. Interesting sandstone piers and gates mark each end of The Diamond boundary, with high railing on a low wall between them. The church forms a powerful and dominating vista from the Castle Street approach, though it is otherwise hemmed in by town buildings.

According to the Ordnance Survey Memoirs, the church is "a neat handsome stone structure 70 feet long by 34 feet wide and capable of accommodating about 300 persons. It has a handsome spire 100 feet high built of sandstone from the collieries. It was erected in 1756 at the sole expense of Hugh Boyd Esq. and adds greatly to the appearance of the town". Thackeray, visiting in 1843, did not refer to the church in his writings, dismissing Ballycastle as not containing much to occupy the traveller.