You would have to look hard to find the thin black line that keeps Scotland moving - a pipeline buried between Cruden Bay and Grangemouth. We start to notice it only when it is switched off, and learn it has been steam-driven all these years. For a two-day strike, not only are the unions getting lots of bang for their strike-pay buck, but the consequences have forced us to ask some big questions about an industry located somewhere over the North Sea horizon.

Who is responsible for keeping the oil flowing? What right have workers to "hold the nation's economy to ransom" over pension changes that many of us have had to swallow? Does Britain face a new mood of industrial strife? What right has one company to inflict "economic terrorism" in a cost-cutting drive intended to demonstrate its management machismo to investors, now threatening not to put their money into the nation's most important industrial plant?

How come we are so dependent on oil? What are we going to do when the forecourts dry up more often, or prices spiral out of reach? Is this a mild taster of a lifestyle that will sharply cut commuter, shopping and food miles?

But this is not all about expecting oil to become more scarce, expensive and politically combustible. It also reflects on how we came to this point with an industry out of sight and mind. In his recent A History of Modern Britain, Andrew Marr argued that North Sea oil is one of the "most remarkable and under-discussed" stories in Britain's recent history. Here was an engineering feat at the frontier of technology greater than anything since Victorians built the railways - "an epic tale of technical skills, bold finance, endurance and individual courage".

Yet where, he asks, is the museum to show the achievements of the industry? Moreover, there are few physical signs of such a mighty economic force. Foreign crude fields may have nodding pumps and extravagant corporate HQs where oil barons flaunt their wealth, but in Scotland there are precious few heroes to tell the story. Sir Ian Wood quietly built a global business round it, but that's about it.

So what legacy is here? In Scotland, you can find a monument to those who died aboard the Piper Alpha 20 years ago. There are further memories of the roustabouts, helicopter pilots and divers who risked, and too often lost, their lives at the frontier of offshore technology.

You might also find a legacy of engineering know-how in Aberdeen, or Heriot-Watt University expertise in extraction from depleting reservoirs. But in Nigg, Ardersier, Methil, Loch Kishorn and Arnish, where the boom in jacket construction came and went Klondyke-style, the hardware floated away and the yards went quiet.

More demanding construction work was done elsewhere, because the boom arrived when British industry was least prepared to handle it. That is the other side of the rarely told story of North Sea oil. Here was a windfall for Britain as prices began to soar and surpass all expectations: the numbers can boggle. The Forties pipeline daily carries black gold worth £50m, with half that revenue bound for the Treasury. It takes only 17 days to fund the Holyrood building, or four months for this year's Scottish Government budget.

Yet Andrew Marr's trawl of political biographies found hardly any mention of North Sea oil. Perhaps it was too embarrassing to admit where the cash was going. This was not a windfall being spent, as in other oil-rich nations from Norway to Abu Dhabi, on trust funds that give permanent returns and are currently trawling globally for assets. British politicians chose to spend it on funding a massive transition in Britain's economy, paying for dole queues while industries collapsed in the 1980s. The point has not been lost on Scottish Nationalists. It was not lost, either, on civil servants in 1974, when they wrote in confidence that the oil boom should be played down because of what it could do to break up Britain.

With oil prices now soaring, the production peak may be past, but the value is not. The Nationalist case can be made that Scotland should have kept all the benefits for itself, though it makes you wonder if it would have been used to avoid necessary change in the industrial base? Thatcherites might argue that the 1980s transition was money well spent. But it is not only Nationalists who think this one-off windfall should have been invested for the future.

Instead, we watch a squabble at Grangemouth over the sharing of the remaining spoils between workers and bosses. This may signal a future of North Sea decline, as ageing kit has to be broken up while pollution is minimised. Shell learned the hard way when its Brent Spar plans attracted international protest. No wonder the forecourt majors are trimming their Scottish operations, with BP out of Grangemouth and avoiding the reputational damage that seems to hold no fear for Ineos.