The Hanois reef is a scatter of granite teeth a mile northwest of Pleinmont, on the wildest corner of Guernsey: Le Grand Hanois, Le Petit Hanois, La Percee, Round Rock, La Grosse Rocque, and Le Bisse, the rock that finally got the tower. Atlantic swells climb these stones and break white against them in even modest weather. In 1807 the Royal Navy lost a vessel here. In 1816 the Marie Elizabeth, a merchant ship out of Copenhagen, went down on the rocks near Rocquaine. After each wreck, islanders wrote letters. They wrote to Trinity House. They wrote to London. The bureaucracy moved at the speed bureaucracies move when the people drowning are not their own. Only in 1851, decades after the proposal first surfaced, did the British government agree to fund the lighthouse, on the condition that Guernsey and Jersey pay the upkeep.

James Walker designed the tower. Construction ran from 1860 to 1862. Lighting reefs that drown at high tide is its own kind of engineering, and the team building Les Hanois introduced something new: dovetailed granite blocks, an interlocking joint borrowed from carpentry, suggested by Nicholas Douglass and refined for stone by his son. The quick-setting cement was a recipe from John Smeaton, the engineer who half a century earlier had built the Eddystone Light in the English Channel. The system worked so well it would be used on Wolf Rock and Bishop Rock after this, becoming the standard for British rock lighthouses. The first flame was lit on 8 December 1862. A seven-hundredweight fog bell hung from the gallery to sound in mist, though as everyone soon admitted, it was not very effective.

Keepers and their families lived in cottages at Pleinmont, on the cliff top, while three men at a time held the tower itself. When sea fog rolled in, the bell tolled every fifteen seconds. From 1915 onwards the keepers added an explosive fog signal, a gun-cotton charge swung outside the tower on a jib and fired electrically. The blast was loud enough that the charge had to be hoisted clear of the windows or the glass would shatter. In 1979 a helicopter pad was bolted to the top, ending the worst of the supply runs by boat in heavy seas. In January 1996 the lighthouse was demanned. Solar panels took over from the diesel generator. The light still turns; it just turns alone.

Today Les Hanois flashes white twice every thirteen seconds, visible to twenty nautical miles. The optic is the second the tower has worn: the original Chance Brothers lens went to a glass museum after a hundred years of service. The funding has reversed too. Guernsey now pays the upkeep, and Trinity House sends a nominal thousand pounds a year, the inverse of the deal that finally got the place built. From the cliffs at Pleinmont on a clear evening you can watch the rhythm: two pulses, then thirteen seconds of dark, then two more, the same conversation the rocks have been having with passing ships since the year Lincoln was president. The reef is still here. The wrecks have stopped.