Les Hanois

Les Hanois reef, a group of rocks to the south-west of Guernsey, are the westernmost point of the Channel Islands. It is the location of a lighthouse operated by Trinity House.

Lighthouse

Les Hanois Lighthouse

Location	Near Fort Grey, Guernsey
Coordinates	49°26′00″N 2°42′00″W
Constructed	1862
Automated	1996
Height	33 m (108 ft)
Fog signal	Sounding Twice Every 60 Seconds (range 2 nmi (3.7 km))
Light
Focal height	33 m (108 ft)
Range	20 nmi (37 km)
Characteristic	White Group Flashing Twice Every 13 Seconds

Les Hanois Lighthouse was constructed between 1860-1862 to a new design by James Douglass, and was first lit on 8 December 1862. It is sited on the rock known as Le Biseau, one mile north west of Pleinmont where the Trinity House cottages were built, and was erected in response to an increasing number of shipwrecks on the treacherous rocks off the western coast of Guernsey. Construction workers were accommodated in Fort Grey.

The tapered granite tower, painted white, is notable in terms of lighthouse engineering because it was the first to be built with all the stones dovetailed together both laterally and vertically, thereby making the construction a single solid mass. The cement mortar in the joints formed between stone faces lock the dovetails so that the stones cannot be separated without being broken. This method, used for the first time at the Hanois Lighthouse, became the pattern adopted for subsequent lighthouses built on sea rocks.

The helicopter pad on top of the lighthouse was built in 1979. The lighthouse was demanned in January 1996 following automation. Conversion to work off solar power required a slowing down of the optic, changing the character of the light, so as to reduce the power requirement and deliver the 20 nmi (37 km) range required.

Its role is to provide a mark warning of the reefs and rocks to the west of Guernsey and providing a position fix for vessels entering the Channel Traffic Separation Scheme.