The 97-foot (30-metre) granite tower, on the summit of Chapel Hill, was designed by Daniel Asher Alexander, and built by Joseph Nelson at a cost of £36,000.

[1] Because the site, Beacon Hill, is 469 ft (143 m) above sea level,[8] the highest base for a lighthouse in Britain, the light was often obscured by fog.

[10] This, combined with poor visibility, may have contributed to the grounding, at Cefn Sidan, of the La Jeune Emma, bound from Martinique to Cherbourg in 1828.

13 of the 19 on board drowned, including Adeline Coquelin, the 12-year-old niece of Napoleon Bonaparte's divorced wife Joséphine de Beauharnais.

In 1842 a new rotating optic was installed: manufactured by Cookson & Co. of Newcastle, it combined dioptric lenses with mirrors and displayed a white flash every two minutes.

This arrangement was replaced in 1857 by a large (first-order) 8-sided revolving catadioptric optic manufactured by Chance Brothers giving the light a range (in fine weather) of over 30 nautical miles (55 kilometres).

[17] As early as 1857, it had been suggested that seafarers would be better served by provision of 'low lighthouses on [the] north and south extremities of island, one with bell, the other with gong or cannon'.

[12] The 3.5-ton lens assembly was the first in Britain to be supported on a mercury trough; manufactured by Barbier & Benard of Paris, it was a first-order revolving four-panel optic in a 'bi-valve' configuration (i.e. 2 sets of 2 panels arranged back-to-back),[19] which displayed a group-flashing characteristic, flashing twice every 20 seconds.

When built the North lighthouse was provided with a two-tone fog siren, housed in an engine house immediately to the north (seaward) side of the tower;[20] it sounded four blasts (low/high/low/high) every two minutes through a pair of upright curved horns mounted on the roof, and was powered by a pair of 16-brake-horsepower (12-kilowatt) Hornsby oil engines (manufactured by Manlove, Alliott & Co.

[27] This new, much smaller optic (made up of four lens panels arranged in two pairs) maintained the old characteristic (flashing twice every twenty seconds) but with a slightly increased range of 19 nmi (35 km).

[7] Between 2019 and 2020 the lighthouse building underwent a major refurbishment, in the course of which the light (provided by a new LED lamp arrangement) was returned to the lantern of the tower.

[32] In 1962 the light was electrified: the paraffin vapour burner was replaced by a 1 kW filament lamp, powered by a pair of generators, and in place of the old lens assembly a much smaller fourth-order optic was installed,[33] flashing once every five seconds (with a nominal range of 24 nautical miles (44 km; 28 mi)).