The West Highlander sleeping-car express - romantic, inspirational and loss-making - is to be axed. Jonathan Glancey joins the protest
This is Monessie Gorge in the West Highlands of Scotland, at 7.45 in the morning: a haunting alley of jutting rocks, rushing water, drifting snow, watchful stags and black-faced sheep woken by the deep- throated alarm of "David Lloyd George", a 1,750hp Type 37 diesel-electric hauling the West Highlander sleeping-car express through braw nature.

In 45 minutes the driver of this Welsh interloper will slow the big engine to idle, exhale hissing, snow-flurrying air from the brakes and bring the five-car train to rest at the buffers of Fort William station, 525 miles and 12 hours from London.

Can this really be the same train that left London's subterranean Euston station under harsh fluorescent light the night before? Not quite. It departed, without a judder, at 8.25 as the joint West Highlander and Royal Highlander sleeping car and Motorail express. In England it sped under electric wires, as Glenfiddich chased McEwan's Export in first-class "lounge cars" and as modern Scottish dainties - Chicken Tikka Masala & Rice (£3.99), Thai Style Vegetables (£3.55) - were tucked under imaginary sporrans.

Somewhere during the night, the train divided. While the Royal Highlander caroused off to Perth and over Drumochter summit (1,454ft) to Inverness, the West Highlander snoozed over Rannoch Moor (1,350ft, and 400 square miles of wilderness) and on through Monessie Gorge to Fort William.

Here passengers, tubby from breakfast, dehydrated by the effects of night- time drams and air-conditioned berths, board the waiting "Sprinter" to Mallaig, the end of the line, where a big, bonny boat operated by Caledonian MacBrayne waits to take them over the sea to Skye; or to Eigg, Rhum or Muck, three purple islands that brood in the black water like a school of humpback whales.

All this is pure Highland magic: here nature and the mark of man - steel rails, viaducts, snow-tunnels and diesel express - are in rhapsodic equilibrium. The West Highlander is one of the most romantic of all railway journeys and the West Highland line, though just 101.5 miles long from Craigendoran to Fort William, a supreme feat of Victorian engineering.

At the end of May, however, the train is to be axed. British Rail and ScotRail say it is too expensive to run; it loses anything up to £3m a year. By reputation, it is reserved for the idle (presumably because sleeping) rich and members of the House of Lords, though you would be hard pressed to encounter a kilted laird or golf-mad Japanese tycoon aboard the 20.25 (Mondays excepted) Euston to Fort William. More likely you will meet walkers imbued with the spirit of Captain Oates, ski parties swaddled in Licorice Allsorts outfits and railway buffs engrossed in Steam World.

Fort William is furious about the big sleep planned by BR for the West Highlander. A fortnight ago, 500 Fort Williamites staged a torchlit parade through the town (pop: 11,000) in protest. Alan Kirk, local restaurateur and unpaid head of the local tourist board, says putting down the West Highlander is the thin end of a wedge that will lead to the closure of the line itself.

"Privatisation has no place for the sleeper or the Motorail service," he says. "Railway management is so disorganised and bureaucratic that we might also lose the steam trains that run here in summer and bring thousands of visitors to the West Highlands. The next thing will be a reduction in daytime trains [three daily to and from Glasgow Queen Street in each direction, the same as when the line opened in 1894]. The fewer the services, the higher the marginal cost of each surviving train, the greater the subsidy needed and the more ruinous-looking the account for the line."

The West Highlander has vociferous supporters all around Britain. The London Friends of the West Highland Line formally constituted themselves only a month ago, but already have a membership in three figures and "600 contacts", including some "pretty high-powered people", according to the group's chairman Hugh Raven.

The group disputes the Government's figures for the money lost on the line. They say that a figure of £453 per head deficit, leaked by the Office of Passenger Rail Franchising, is a wild exaggeration. Their own estimate is that the service needs a maximum of £43 per head subsidy to cover present operating costs, and that the subsidy needed could be as low as £4. Hugh Raven also says that he knows of many examples of passengers being turned away when the train was not full, suggesting that the service is deliberately being run down.

The West Highland has never made money. It has always been accepted as a "social" line. A reporter for the Glasgow Evening News wrote in 1894, "for mile upon mile of its length, not a single vestige of human life is to be seen. Its very stations are simply names - oases in a barren moorland. A paying traffic must be a matter of slow growth."

It had been a major investment: in the 101.5 miles from Craigendoran, where the West Highland line branches on to its own tracks, 5,000 navvies built no fewer than 350 viaducts and underbridges and 50 overbridges. They laid tracks up and over the treacherous bogland of Rannoch Moor where the West Highlander is brought down to speeds of 25mph, or even less, in rainstorms and blizzards.

Militant Sabbatarianism meant that for many years there was no traffic on Sundays. The luxury homes that directors of the North British Railway imagined would spring up besides the railway banks of Loch Long (sea water) and Loch Lomond (clear water) bringing Glasgow commuter traffic to the line never materialised. But the West Highlander did bring fish to Billingsgate and hikers to the Highlands. It carried schoolchildren, wood pulp, forestry equipment and the Royal Mail (it still does). It once gave a lift to a golden eagle, the great bird settling on the buffer-beam of a North British "Glen" class 4-4-0. A baby boy was born on a Glasgow-bound train one day in 1935 and, yes, there was a doctor on board.

On my journey there is a Highlander with straggling hair and a ribbed brown and orange jumper who makes it whisky-clear that he can do this journey quicker by car, but says "aw, ye don't understand, man" when asked why he is travelling by train.

And there is my cabin mate, a builder from Connemara on his way to Scotland to do a bit of navvying much like his predecessors; shoulder to shoulder with Gaelic-speaking Scottish islanders and itinerant Scandinavian labourers, they built the West Highland line in the early 1890s, working 70 hours a week and sleeping in turf huts. "Not a laird then?" I ask, clambering into the top bunk (brown blankets, a courtesy bottle of Highland Spring Water and just about enough room to swing a gerbil). "No, pal; builder. Been using the sleeper for four years. Four double vodkas and a good night's kip. Can't do that on the plane or car, can you?" He sleeps like a baby, and in the morning when I duck out of the cabin to photograph the train negotiating Monessie Gorge, he sticks his head out of the blankets and says, "It's been a pleasure sleeping with you."

"You must meet some characters," I suggest to Ken Lightfoot, chief steward, as the train twists into Fort William. "Tell me about it," he says, still fresh and chatty after more than12 hours on the go. "The times I've been asked to write a book about it, I can't tell you." And he doesn't.

The West Highland is a line with a special heritage. By bunk or kennel (£25 a head, human or canine), a trip on the West Highlander is idiosyncratic and inspirational. No hotel can rival breakfast on the move through Monessie Gorge. Sadly, the West Highlander cannot be shunted into some neat business account. It is out on a limb. That is why it is going and, equally, why Fort Williamites and the London Friends are fighting for its future. Should they succeed, mythical lairds, Irish builders, walkers, climbers, twitchers, tourists and railway enthusiasts will dream on, with a little help from "David Lloyd George", in a land that remains, today, as remote from London as Central Africa was a century ago.