There's not much call for lighthouse keepers these days. Technology has done for these lone guardians of the flame; the last manned lighthouse in the UK, North Foreland, off the coast of Kent, went automatic in November 1998. But the writing was on the whitewashed walls of these stony sentinels long before then.
Bonfires and beacons on cliffs and promontories like those mentioned in Homer's Iliad and Odyssey did the job for centuries - the remains of a Roman lighthouse can still be seen (by tourists, though not ships) at Dover - but none of them matched the 440ft-high Pharos at Alexandria, Egypt, one of the seven wonders of the world. Built in the third century BC, it lasted 1,500 years.
Not all lighthouses were so durable. The first one to be built on the treacherous Eddystone rocks, 14 miles off Plymouth, in 1690 was swept away soon afterwards and the second burnt down. The third, built by John Smeaton in 1759, was the first such structure made of stone, and pioneered dovetailed rock construction techniques. But it relied on the very old technology of candles - 24 of them in a chandelier - to warn passing boats.
Oil fires and gas-powered lamps were the guiding lights of the 19th century until they were replaced by football-sized light bulbs in one of the first applications of electricity. Magnification was achieved through a series of lenses - supported on a bed of mercury, sometimes leading lighthouse keepers to madnesswith mercury poisoning - that were rotated to produce the flashing effect.
Lighthouses have been both the scene and inspiration of heroic stories, like that of Grace Darling, the Farne Isle lighthouse keeper's daughter who rowed through stormy seas to save shipwrecked sailors. Their faraway light, symbolic of guidance, steadfastness and hope, illuminated famous novels of the Twenties such as Virginia Woolf's To the Lighthouse and F Scott Fitzgerald's The Great Gatsby.
By the 1960s helicopters were delivering supplies to offshore lighthouses but, ironically, their arrival meant the days of permanent keepers were numbered. Trinity House, the royally appointed authority responsible for seafaring safety, established by Henry VIII's charter in 1514, still looks after Britain's 72 lighthouses. But if you see one with a light on, there's unlikely to be anyone at home.