Toomebridge Lock, Toome Canal, Railway Road, Toomebridge, Co Antrim, BT41

Toomebridge Lock is the first of five locks on the Lower Bann Navigation, a canal system running from Lough Neagh to Coleraine constructed by the Board of Public Works between 1847 and 1859. The lock is situated along an extensive artificial cutting running parallel with the River Bann on its east bank, positioned just downstream from the sluice gates that maintain the water level of Lough Neagh. It enables boats to negotiate a water level drop of approximately 90 centimetres (3 feet) created by these gates.

The lock was designed by John McMahon, the Board's Engineer. The Lower Bann Navigation scheme was devised not only to improve navigation but also to alleviate flooding through dredging the river, removing rock shoals, and lowering the level of Lough Neagh by approximately 1.8 metres (6 feet). Upon completion, responsibility for the lock passed to the Lower Bann Navigation Trust; in 1929 this transferred to the Ministry of Finance and eventually to the Department of Agriculture for Northern Ireland. Since 2000, Waterways Ireland has held responsibility.

The lock comprises a single chamber measuring 6.25 metres (20 feet 6 inches) wide. It is lined with brick and topped with a course of dressed stone blocks and kerb. Its quarter-round ends, beyond the gates, are constructed of bolstered masonry blocks laid in regular courses. A pair of timber lock gates stands at each end. Each gate incorporates a vertical paddle (sluice gate) manually operated through a two-step rack-and-pinion mechanism. The gates have been replaced over time and are not original; they were refurbished in 2005 along with new balance beams and heel posts. Recesses in each wall immediately above the upper gates indicate the former presence of land paddles (ground sluices), apparently abandoned in favour of the present gate paddles because frequent blockages by flotsam made them unreliable. The paddle mechanisms are accessed along cantilevered metal and timber footbridges affixed to the upper sides of each gate, which also provide access to the west bank of the lock chamber. Stop plank grooves situated just beyond each pair of gates were used to seal off the chamber during repairs and maintenance. Depth gauges calibrated in feet and inches are set into slots on the west side, with galvanised metal ladders positioned in the south-east slot and up the middle of the east side of the chamber.

The setting includes three cast concrete mooring posts and a lifebelt post along each side of the chamber. Modern metal signs advertising opening hours are positioned at the north and south ends of the west bank. The ground along the east side is surfaced in tarmacadam with a low concrete curb running approximately 2 metres in from the chamber edge. A modern galvanised metal barrier separates the lock area from a public footpath running along the east bank of the canal. The ground west of the lock is grassed and delineated by a modern galvanised palisade fence, with a gate providing access to a concrete footpath leading to the weir and sluice gates controlling Lough Neagh's level. Concrete steps at the north-east end lead down to a steel footbridge accessing a landing pontoon; the bank has been cut away slightly with gabions installed to accommodate it. An identical pontoon accessed by concrete ramp and footbridge stands at the south-east end. These floating landing jetties (pontoons) were added in 2004 to 2005.

A lock keeper's house stands some distance north of the lock, close to the former railway bridge. The original single-storey structure was replaced in the 1960s with a modern building having a pitched concrete tile roof, uPVC gutters, cement-rendered walls, and square-headed openings with uPVC fittings.

Apart from the Newry Ship Canal, the Lower Bann Navigation is the only operational canal in Northern Ireland, making this rare example of a working lock of considerable significance.