Suddenly I see it: a lighthouse. And I am excited. I used to be a lighthouse keeper, very briefly, although for most of my adult life I have been involved in the world of university art schools. Over the years I have found myself, in a professional role, travelling along the Grand Canal to review the Venice Biennale, or on a hydrofoil from Hong Kong to Macau to examine a PhD candidate, or in Boston Harbor desperately seeking a lecture venue. And then there it is, white and pristine, with the sun setting or rising behind it.

My mind always concertinas back to the early 1970s and my introduction to "the service". These surprise sightings of lighthouses, often close to an inner city, don't just take me back to my own youth, but to a shared landscape. If the Vietnam War was the backdrop, the stage was filled with such disparate events as the Watergate hearings, the deaths of Jimi Hendrix and Janis Joplin, famine in Biafra, Nasa space flights and the fading of Harold Wilson's "white heat of technology" into the darkness of the global oil crisis.

I was 19 years old when I was interviewed in Edinburgh for the job of relief keeper by the Commissioners of Northern Lighthouses. I was just another art student looking for a summer job. My hair hung well below my shoulders, I had a great set of Captain Beefheart records and I walked about with a permanent grin on my face as I had recently, finally, lost my virginity. I rolled my own cigarettes, was a member of Amnesty International and had just read Jack Kerouac's Desolation Angels. In short, I was eminently suitable for the job. Or so I thought.

At the time, I was a student at the wonderfully named Duncan of Jordanstone College of Art and Design in Dundee. The art school pub, The Tavern Bar, sat beneath a row of soot-covered tenements just behind the brutalist architecture of the art school itself. It was outside "The Tav" one particularly beer-fuelled Friday that my classmate May Kirkland asked me what job I would most like to do in the whole world. I sensed she wanted an immediate answer, so I blurted out: "I've always wanted to be a lighthouse keeper. Almost as good as being a spaceman." And that, I thought, was the end of the matter.

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Not so. A few days later, May came into the life-drawing class with an advert for full-time lighthouse keepers from that morning's edition of The Scotsman newspaper.

"Why don't you write in and see if they take students on for the summer?" she tempted me, like a siren from a rock. And so I did. That's how, a few weeks after my interview, having just turned 20, I found myself heading off with a backpack full of poetry books and a cassette player the size of a big-city phone book for my first lighthouse, on the tiny island of Pladda, off the much larger island of Arran, off the west coast of Scotland.

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I'd checked out exactly where it was the night before, in my father's Times Atlas of the World. It was about the size of a biscuit crumb. Closer inspection revealed it was in fact a biscuit crumb and underneath was an even smaller dot. This was going to be my home for the next few weeks.

All around the British Isles, other young students - geologists, poets, marine biologists - were setting off on similar adventures as relief keepers, each constructing a personal coming-of-age narrative.

I can't say I knew a lot about lighthouses. I imagined they were like candles on a Christmas tree, designed to bring cheer to those living in the more remote parts of the coast. But I soon came up to speed under the tutelage of three different generations of men: each of them had fought in their generation's war, and then lived exciting lives around the world before "retiring" into the Lighthouse Service. I learned how to light the paraffin lamp (turn on the vapour, stand well back and cause a controlled explosion in the light chamber); how to wind up the light every 30 minutes (a lighthouse is like a giant grandfather clock with a weight that descends the length of the tower); and how to pump up the air pressure to the paraffin every 20 minutes. Strangely, paraffin provides a stronger beam than electricity and in the early 1970s was still used on some of the bigger lights.

Being a lighthouse keeper was one of the few jobs where you were paid to tell stories. The night watches (or "Rembrandts", as I dubbed them) started at 10pm, 2am and 6am. Like the light, they rotated nightly, so you never did the same watch two nights in a row. The keeper going to bed at 2am would stay up an extra half hour, having prepared a fresh pot of tea and some cheddar cheese on digestive biscuits, and tell stories to the bleary-eyed keeper who was just waking up; tales of working in Australian gold mines or driving Harley-Davidsons across the US. No matter what watch you were on, everyone had to be up for breakfast at 8am, so some nights you had little more than an hour's sleep at a single stretch.

During the day there was plenty of work to be done. One keeper cooked delectable meals while the other two carried out various duties around the island. My three lights were all on uninhabited islands. On Pladda we had to paint the tower white, build a road and help to shear the sheep that the farmer on Arran, who was also our boatman, kept on our tiny island. On Ailsa Craig, a huge mountain of a rock halfway between Glasgow and Belfast known as "Paddy's Milestone", we created a vegetable garden and dined on the lobsters we pulled from the sea.

My final posting was to Hyskeir in the Inner Hebrides. I arrived by helicopter to find a tiny strip of lava with a lighthouse at one end and a foghorn at the other. On my last morning there we had to clear hundreds of dead birds off the flat roofs of our accommodation. They had flown into the light the previous night, in a sad, premature end to their migration to Africa. Tens of thousands of others had spent the night circling in the beams of the light before continuing south.

Eventually, I was to tell the whole story of my lighthouse summer in a book called Stargazing: Memoirs of a Young Lighthouse Keeper (2003). I started writing it in the mid-1990s around the time the last remaining manned lighthouses around the world were being automated. And so lighthouse keeping became one of the first professions to become totally redundant. You still find some flesh-and-blood blacksmiths, or builders of dry stone dykes, or manufacturers of barrels. It is still possible to buy VHS tapes and 35mm slides. But lighthouse keepers are all gone, forever.

These days, thousands of people around the world go "lighthouse bagging" the way others go birdspotting. And every year over International Lighthouse and Lightship Weekend, actors dress in heritage costumes and assume the roles of lighthouse keepers and their families. We used to groan at the thought that one day this might happen. I blame Princess Anne, the Princess Royal. She has been known to bag as many as five lighthouses in one day and is a keen promoter of the activity.

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I prefer the term "horizontal mountaineering" - leaving a big city and gradually heading to a rocky outcrop as towns, villages and lonely farms give way to a white tower and a fine sea view. But there are no people there any more, no tales being told at two in the morning by a coal fire. No one to remove the dead redwings and wrens from the flat roofs. And the lighthouses themselves have become glorified traffic lights. They are switched on and off automatically and serviced, if at all, by engineers in helicopters. The cosy outhouses where we used to live are now home to rats and mice, the windows broken, while the paint flakes on the formerly pristine white towers.

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There are lessons to be learned from the demise of this once-honoured profession, not least by universities. It is a profession that predates the Great Lighthouse at Alexandria and has taken many strange forms, including the Statue of Liberty in New York, run by the United States Lighthouse Service. Most of the men I worked with (and sadly they were all men, mostly with families on the mainland) could see their own redundancies coming from a couple of decades away, like an administrative pirate ship on the horizon.

If you had asked me in 1973 what I would be doing in 2010, I would probably have thought myself lucky to be alive. Vietnam was escalating, the Cold War was hotting up, and no one seemed to be interested in doing anything about pollution, nuclear stockpiles or oil shortages. I'd watch yachts sail past our island and wonder why we could not harness the wind. I'd feel the rocks hot under my hand - even in Scotland - and wonder why we could not capture that heat. Impotent to do anything, I decided to turn my life into an adventure.

I'd always enjoyed reading Robert Louis Stevenson, especially his adventure stories, and Treasure Island was at the top of my list. But it wasn't until later in life that I discovered the role his family had played in designing and building some of the world's greatest lighthouses. One of the classics was the Bell Rock off the east coast of Scotland, a dramatic sight rising straight out of the sea. I worked with several keepers who had served on it. Before this great feat of engineering, the local abbot had placed a bell on the treacherous rock to warn ships of its presence, as hundreds had foundered there on stormy nights.

"The beds were like coffins; they had sides on them to stop you falling down the tower," my colleague Finlay told me during one early morning Rembrandt on Pladda. "We slept in the tower and there was a round hole in the floor and ceiling for the weight to drop through. Every half an hour it would zip past your head as the keeper on duty wound it back up. Drive you crazy, so it would."

Many decades later, I found myself chairing a session at an academic conference in Canberra during a fiercely hot Australian summer. The conference was about outlaws - everyone from Ned Kelly to Bonnie and Clyde. I was in a taxi with a colleague, grumbling at Scotland's inexplicable omission - it could have been so well represented by Rob Roy MacGregor. My colleague got out at his hotel and I turned my attention to the taxi driver. He was a very large Pacific Islander and further questioning revealed he was from Samoa.

"What was it like growing up there?" I asked as we drove to my hotel.

"It was a great childhood. Every morning my brother and I used to run up the hill behind Apia to the tomb of Robert Louis Stevenson. It was up behind the old lighthouse. My people called him 'Tusitala', the teller of tales."

I was hooked. I had to go there - not just the great Stevenson, but a lighthouse, too! And so it was that between my Wednesday morning studio class at the University of Melbourne, where I worked at the time, and my Monday PhD supervision sessions, I jumped on a flight via Auckland and Tonga and found myself in the middle of the Pacific.

I'd made an online booking at the legendary Aggie Grey's Hotel down on the waterfront. Everyone from Marlon Brando to Somerset Maugham had stayed there in the lap of Samoan luxury. I could afford only the modern wing, a bit like a Best Western with palm trees. I didn't even get water views as the cheapest rooms looked the other way. But I was happy, for they looked towards the hill - more like a bloody great mountain - and the tomb of Tusitala.

The next morning I pushed my way through the deep jungle growth that bordered the large house called Vailima - not unlike the cricket pavilion at Lord's, I thought - where Stevenson had lived in great luxury, and I clambered to the top in killing humidity. Breathless, I arrived at his final resting place with his own immortal words chiselled on the tomb: "Home is the sailor, home from the sea, and the hunter home from the hill."

I was totally alone, high above a lighthouse, gazing out across the great Pacific, and my whole past seemed to open up before me.

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