The light was built to replace the lighthouse in the centre of the island of St Agnes and helps vessels to enter Hugh Town harbour, via St Mary's Sound.

It was first lit in 1911, is circular, 45 feet (14 m) tall and consists of a black steel open lattice foundation, white gallery and black–domed top.

Initially, the lamp used was an incandescent burner which was powered by oil gas; the fuel was kept on site in four pressurised tanks (with a total capacity of 700 cubic feet), which the local Trinity House vessel would keep replenished.

The rotating third-order optic was driven by clockwork; it displayed a white flash every 20 seconds and its beam had a range of 16 nautical miles (30 km; 18 mi).

[5] In late 2011, the year of its centenary, the lighthouse was updated, and at the same time downgraded (its visible range being reduced from 17 to 9 nautical miles (17 km; 10 mi) in accordance with the Trinity House 2010 Aids to Navigation review).