Stevenson, the great Scottish lighthouse engineer and grandfather of Robert Louis Stevenson, designed dozens of lights around the rocks and headlands of Scotland. Barra Head was among the most demanding. James Smith of Inverness built it. The light was first exhibited on 15 October 1833, oil-burning and tended by keepers who lived on a cliff edge at the end of the inhabited world. The granite for the tower came from a small quarry on the island itself, set into the gneiss bedrock that makes up most of Berneray. Stand at the lantern room and the Atlantic stretches uninterrupted to the western horizon. There is nothing between you and Labrador.

Mariners running the western seaboard of Scotland needed a marker for the southern mouth of The Minch, the long sound between the Outer Hebrides and the mainland. Barra Head Lighthouse sits roughly halfway between the Eilean Glas light on Scalpay to the north and the Rinns of Islay light to the south. Its range is 18 nautical miles. In clear weather that is enough to bracket the approaches. In Hebridean weather, which is rarely clear, ships needed every flash they could find. Atlantic storms strike Berneray without preamble. There is no shallow water to the west to break their force. Fish have been thrown by waves onto the grass at the cliff top, hundreds of feet above the sea.

The crofting families of Berneray and Mingulay left between 1910 and 1931. With them went the regular boat traffic that had supplied the lighthouse for nearly a century. Fog and mist made flag and lamp signalling unreliable. By 1925 a wireless link to Castlebay on Barra solved the communication problem. Then war came. In the late 1930s the pier was rebuilt to land hundreds of steel girders and reels of cable for three large radar masts, part of the network that guarded the Western Approaches. A Scots Derrick, a stiff-legged crane, was erected to lift the masts ashore. A Blenheim bomber crashed into the cliffs nearby during the Second World War. The wreck was not found until years later, by a rock climber working the gneiss.

Automation came to Barra Head on 23 October 1980, when the last keepers were withdrawn. The oil-burning light had been converted to incandescent in 1906. Now it would run unattended, an electric flash on an empty island, watched by sensors rather than by men. The keepers' cottages remain. So does the small cemetery where keepers and their families were buried, on a hillside that overlooks one of the loneliest stretches of ocean in Europe. The lighthouse still works. It still marks the southern entrance to The Minch. But the cliff is now empty of human voices, and only the wind remembers what it was like to live here.