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Origin and history

The Penfret lighthouse, built between 1836 and 1838 on the eponymous island of the Glénan archipelago (comune of Fouesnant, Finistère), is a white pyramidal tower of 18.80 meters, culminating at 33.30 meters above the sea. On October 1, 1838, it became the first French lighthouse equipped with an oil steam incandescent burner in 1898, before its electrification in 1951 and automation in 1993. Its total cost is 42,000 francs, with an authorized budget of 43,583.91 francs.

The adjacent fort, built from 1841 to 1847, incorporates the lighthouse into a 41 x 23 metre rectangular enclosure surrounded by a 4 metre wide dry ditch. This unique military shed combines a crenelated guard for 60 men and a battery in three 90-metre sections, connected by an underground passage. The materials used — local granite and Trégunc — are partly from the excavations of the ditch. The battery, originally planned for three 30 pound guns and two mortars, was modified during World War II by the German occupation, which installed anti-aircraft parts.

The island of Penfret, strategic for its freshwater wells and protected anchorage, is coveted from the 18th century. In 1755, the engineer La Sauvager proposed a battery, without suite. The defence commissions of 1818, 1825 and 1836 reiterated this need, leading to the joint construction of the lighthouse (1836–38) and the fort (1841–47). The land, originally ceded for free by François-Adolphe Théroule (owner of the Glénan) in exchange for its post-military retrocession, was finally expropriated in 1859 for 4,000 francs. The site, classified as a historical monument in 2017, is now maintained by the Plein Phare association on Penfret.

During the First World War, a submarine defence post (PCMSP) was installed there in 1918. In 1939, a special battery of four 95 mm guns was deployed. Under the occupation, the Germans turned the guard corps into barracks and dismantled a clutch to facilitate access. Since 2012, the fort, owned by the Lighthouses and Balises, has been restored by the local association, while the battery, belonging to the Coastal Conservatory, remains abandoned.

The lighthouse, still in operation, has been remotely controlled since 1993 in Concarneau. Its truncated pyramidal architecture, coupled with a technical house, and its red lantern make it an emblematic maritime landmark. The fort, with its ten steeps and its masonry steep ditch, illustrates the adaptation of 19th century coastal fortifications to island constraints. Together, listed as historical monuments in 2015 and then classified in 2017, it bears witness to the military and maritime history of Brittany.

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