Sinclair Seamen's Presbyterian Church, Corporation Square, Belfast, BT1 3AJ

Sinclair Seamen's Presbyterian Church is a stone church built in 1857-58 to designs by the architectural practice Lanyon Lynn & Lanyon. It stands in Corporation Square, Belfast, facing the Harbour Office in what was the original home of Belfast's shipbuilding industry. The church was commissioned by Thomas Sinclair in memory of his father John Sinclair, a Belfast merchant, and was built specifically to serve mariners visiting the port of Belfast.

The building is constructed of uncoursed ashlar sandstone in the Italianate style. Its plan is distinctive and unusual: it is L-shaped and encloses a freestanding square campanile tower, which is linked to the church by an arcaded bridge functioning as a flying buttress at balcony level. The tower rises to approximately twice the height of the church itself.

The main frontage to Corporation Square features a shouldered gable with three recessed panels decorated with machicolated friezes. The central panel contains a rose window, while smaller oculi occupy the outer panels. A dentilled cornice runs along the top, and a stone roundel below the rose window formerly contained lettering identifying the church. Entry is gained from the side through an archway beneath the staircase link to the tower, which is lit by an arcade of lancet windows.

The square bell tower is notable for its architectural treatment. Two tall machicolated panels on each elevation are pierced by arrow-slit openings. At the top stage, the belfry is screened on all four elevations by large paired Venetian Gothic windows with central quatrefoils and slender colonettes, capped by a shallow pitched roof. Lead covers the tower; slate covers the main church roof.

The west elevation facing Corporation Street is similar to the front but simpler in treatment, framed by the side chapel to the north and the tower to the south. The north elevation (rear) would have been similar to the front with a shouldered gable, rose window, and three lancet windows below, but is now largely obscured by a later two-storey extension housing church halls. The east elevation is plain, having been previously abutted by adjacent building.

The interior is richly and eccentrically decorated with an unusual and historically significant collection of nautically-themed stained glass windows, monuments, and ship models, giving the church a unique character reflective of its original function as a church for mariners. Much of this additional stained glass and the memorials largely date from the ministry of Reverend Samuel Cochrane between 1902 and 1945. The windows are leaded and stained glass throughout.

The church retains much historic fabric and detail of quality. Iron railings on dwarf walls and associated gates and steps form part of the listed extent, though these are not original, as confirmed by early photographs. The architectural practice Lanyon Lynn & Lanyon is notable in local history, and this church represents an unusual and fine example of their work, distinguished by its distinctive style, proportions, ornamentation, and plan form, as well as the exceptional quality and survival of its interior arrangements.