Aberdeen is booming.

By way of evidence I offer Union Square, the cavernous mall, opened in 2009, which separates the train station from the ferry terminal. On a sun-blessed, midweek afternoon shoppers are out in their droves. It is the United Nations en fete; long gone are the days when the Granite City's population was no more ethnically diverse than Greenland's. There are jobs aplenty, and distance and unfamiliarity with the Doric tongue are no hindrance to those seeking them. They must be well recompensed for their effort, for Aberdeen is the most expensive British city outside of London in which to find a bed for the night.

Twenty-five years ago it was not unusual to read of the city's imminent decline. It was confidently asserted that oil - the "black gold" under the North Sea - would soon run out. What a difference a few years make. I lived in Aberdeen in the early 1970s when oil was beginning to gush out like coins from a fruit machine. It felt as if the whole place was throbbing and about to burst. Long-jawed men in stetsons and cowboy boots could be seen swaggering into - and staggering out of - bars, and Harley Davidsons roared down Union Street as if it were the main drag in Houston, Texas. On Saturday nights you could emerge from the cinema and witness scenes akin to those in a Clint Eastwood movie.

Then, oil was viewed by many as the panacea for all ills. Like some elixir, it would cure our social and industrial ailments, compensating for the tens of thousands of jobs lost in coal-mining, shipbuilding and steel-making. "It's Scotland's oil" was the cry. But that was an aspiration, never a reality. All of the revenue it produced was siphoned off by the Treasury and precious little of it made its way back north. As one nationalist bitterly put it: "Scotland must be the only country on Earth to discover oil and become worse off."

But I am only passing through, bound for Shetland, from where much of Aberdeen's wealth trickles down. My newspaper tells of another soon to be exploited field with enough oil in it to keep the ball rolling for a few more decades. About one-fifth of the oil and gas thought still to be found off the UK coast is believed to lie to the west of Shetland. Sullom Voe, the hub of the industry, remains one of Europe's biggest oil terminals, piping some 20 per cent of the oil that flows through the island. Irrespective of the price of a barrel, it is revenue that everyone wants to get their hands on, not the least of whom are Shetlanders. For them, it's not Scotland's oil, but Shetland's.

The MV Hjaltland inches toward the open sea. It's like threading a needle. The channel is narrow and as choked with vessels as Princes Street is with buses in the rush hour. Where fresh and salt water meet there are dolphins doing party tricks for the tourists, many of whom gather on deck to take pictures. Barbara is from Kent and has travelled the length of Britain to catch the ferry, which she made by the skin of her teeth after her camper van threw a wobbly en route. Why is she going to Shetland? "I've never been before." We are joined by a man in his fifties from East Lothian who is employed on one of the rigs. He does two weeks on, two weeks off, though when business is bad he sometimes has to take three weeks off. He doesn't seem to mind. With so much free time, he's often abroad, picking up cheap deals to Spain and Portugal. "It takes 14 hours to get from Aberdeen to Lerwick," he says, "and it's 15 hours from Edinburgh to Las Vegas." Nor, he adds, is there much difference in terms of cost. You don't need to guess where he'd rather be heading.

The travel writer Jan Morris called Shetland "the inset islands" because on maps of Britain they are invariably relegated to a box on the corner of a page. "This has subtly affected our concept of them," wrote Morris. "They are much, much further away than most people suppose. They are much more foreign places, much harder, older and more distinct." This is patently true. The nearest mainland town is Bergen in Norway. Indeed, many Shetlanders prefer to align themselves with Norway rather than Scotland and Anderson High School in Lerwick offers classes in Norwegian. Moreover, the Vikings, despite their reputation for ravishing and pillaging, remain an indelible part of Shetland lore, not least for their adventurousness and resistance to external influence. To live this far from "civilisation" requires a combina-tion of independence, resourcefulness, bloody-mindedness and wit.

Nor, as one islander tells me, do they feel any more affinity with the powers-that-be in Scotland than in England. "In London they don't care about us, in Edinburgh they hate us," he says. In 1979, Shetland's inhabitants made plain their distrust of the Central Belt and rejected devolution by almost three to one. In 1997, however, they voted by a considerable margin not only for a Scottish parliament but one with tax-raising powers. If that seems a remarkable volte face perhaps it was. But it may be explained by the fact that come 1997 the LibDems supported it. If there is a safe seat anywhere in Britain for Nick Clegg's embattled disciples it is surely here, where you can't get further away from Westminster.

In the morning smirr Lerwick looks grey and, if truth be told, rather grim. Dominating the harbour and obscuring much of the immediate hinterland is the Sans Vitesse, a huge, zebra-striped accommodation barge for oil and gas workers which is impossible to avoid. Fat gulls swoop and screech and the air smells oily and fishy. The old, higgledy-piggledy parts of Lerwick, with shops selling Fair Isle woollens and fiddle music, have charm but offsetting these is a jumble of jerry-built buildings by the shore whose purpose can only be utilitarian.

There are no Yes or No signs in windows, though the Shetland Times has a lively letters page on the referendum and a few related stories. Apparently pupils at Anderson High School have said a "big 'no' to independence" in a mock referendum, which the Better Together spokesman, Geordie Jacobson, says mirrors similar events in other schools in Scotland. However, this is countered by Yes Shetland's chairman, Brian Nugent, who recalls that in a debate earlier in the year in the constituency of Alistair Carmichael - Secretary of State for Scotland and ardent No man - a majority of people said they intended to vote Yes.

The ferry from Lerwick to Bressay takes five minutes and charges foot passengers £5.20 for a return journey. On board is a woman who has lived on Bressay for 40 years, having met her husband, a Shetlander, in her native Peru. There are also two Swiss tourists, upset their team is out of the World Cup but amazed by the Germans' 7-1 thumping of Brazil.

I have come to see Jonathan Wills, who as a student at Edinburgh University in the 1970s, was a flatmate of Gordon Brown. Like many islanders Wills is a juggler. In the summer months, through his company Seabirds-and-Seals, he takes visitors by boat to view wildlife. Come winter, he writes books for children. He is also an independent councillor, as all councillors are in Shetland. Having supported Labour throughout his adult life, and been a member of the party, he currently sides with the SNP and is pro-independence.

"Labour left me," he says, explaining why he has swapped allegiance. "Shetland is going to vote No by the look of it," he adds.

"I think it's a mistake. There's a reluctance to accept that Shetland is a county of Scotland. Shetland has done very well out of the Scottish Government.

"But there's this fantasy that we are Scandinavian. I find this Viking thing a complete turn-off. Who wants to be associated with genocidal ethnic cleansers? We're a mixed and cosmopolitan society."

We take a stroll round his lush garden which butts on to the shore. In a disused barrel there is a nest with newly-hatched starling chicks. Geese parade in a nearby pen. "An otter got my goslings," says Wills. The sea looks serene and inviting. It's The Good Life incarnate. Contrary to prevailing opinion, Wills says it is possible for trees to grow on Shetland, all they need is protection from the ever-present wind. If anything, wind is an issue which divides Shetland's 23,000 population even more than the possibility of independence. As we chat Wills receives the news that an Edinburgh court has given the go-ahead for a controversial, 103-turbine wind farm - one of the biggest in Scotland - which will be built in part of the island that at present is moorland. Wills is delighted. Others less so. Though it has been estimated the development could bring Shetland an annual income of £30 million, protesters insist that the damage to the environment is incalculable and may be irreparable. It is an argument that has been raging for several years and will doubtless continue.

The road to Hillswick passes through the area where the turbines will be erected. It is not a picturesque landscape and has been shorn of natural vegetation by ever-voracious sheep. There are few cars but there are signs of dissent at regular intervals. These are not, however, directed at the wind farm. What they are fearful of is the closure of local schools. "Closing Schools Kills Communities" reads one; "Close No Nort Schools" says another. The Shetland Island Council has tough decisions to make and the education budget is ripe for pruning.

Tom Morton lives with his family in a white-washed former manse at Hillswick, which is near the point of no return. Lerwick lies 30 miles to the south; Isbister, 15 miles to the north, marks the end of the road. Thereafter all that's left of inhabited Britain are the islands of Yell, Fetlar and Unst. In an email Morton put me on "very large slobbery-but-harmless dog alert". Rarely have I seen a bigger one. There is a large walled garden to protect fruit and veg against the elements and a hot tub awaiting construction. Like Wills, Morton is a multi-tasker. He writes books and songs, was the first non-DC Thomson employee to script The Broons and Oor Wullie, and now edits the monthly magazine Shetland Life. He also presents a music programme, Morton At Midnight, for BBC Radio Scotland, broadcasting from a room in his attic which he has converted into a studio. "On Air" says the sign on the door to deter unwelcome guests, of whom there can't be that many to whom he is not related.

"Shetland," says Morton, "is going to vote No by a colossal majority. It's as near a dead cert as you can get."

His wife Susan joins us for lunch in the cosy, flagstoned kitchen. She shares her husband's antipathy to independence, concerned - as a GP - about the wellbeing of the health service and about her pension. "I'm 10 years from retirement and nobody can tell me what's going to happen to my public sector pension." So perturbed is she that she has considered the drastic step of moving to the north of England. From the way she talks it's clear that in Shetland the argument over the referendum has been deeply polarising and peppery. Her husband characterises Yes campaigners as "a small group of highly motivated romantics".

There are a couple of hours to go before the Hjaltland makes its return trip. In Lerwick's narrow main street teenagers gather to perform songs from Cats prior to a forthcoming show. It is their future that is up for grabs. Better than most of their peers elsewhere in Scotland, they are accustomed to flux and uncertainty. After all, this is a community formed of immigrants, as the Incoming Project at Shetland Museum emphasises. Not that those who come here always find a hearty welcome.

In that respect Shetland is no different from the rest of the country. But what is apparent is that the distance between the island and the mainland breeds suspicion and the need for self-sufficiency. Shetlanders know what it's like to be forgotten; to a degree, they expect nothing less. Neglect is what they thrive on, and thrive they have, with unemployment at one per cent. They have learned through experience to go with the flow and adapt accordingly. Oil or no oil, something always turns up. n