Perhaps the most notorious injustice ever committed by the UK government against Scotland (with the possible exception of the infamous “40% rule” in the 1979 devolution referendum in which the dead were counted as No votes) was the suppression for 30 years of the McCrone Report, which revealed how wealthy an independent Scotland would have been after the discovery of oil in the North Sea.

Successive Labour and Conservative governments at Westminster frantically fought to deceive Scots over the value of the bounty for decades. And now, on the eve of another referendum, it looks like they’re about to try it again.

The No campaign has made a great deal out of last year’s abnormally low tax receipts from oil – which were largely due to record levels of investment being made by oil companies and offset against tax – in order to make Scotland’s future financial prospects look worse than they really are.

It’s remarkably reminiscent of how Unionist politicians told Scots in the 1970s, 1980s and 1990s that the oil would run out in just a few years and wasn’t anything to get excited about. Inconveniently, however, the reasons for 2013’s record investment have begun to leak out before the referendum, and the news is dramatic.

Exploration projects have recently revealed some of the biggest and most potentially lucrative finds in the North Sea’s history. The Clair Ridge and Bentley fields look set to provide hundreds of millions, or even billions, of barrels. Other areas – including ones previously blocked by the UK government to avoid interfering with the operation of Trident nuclear submarines – also offer promising returns.

Once again, Westminster has desperately tried to talk down the significance of the finds, as noted by the Investors’ Chronicle last month:

When highly respected oil-industry figure Professor Sir Donald Mackay – a former economic adviser to the Secretary of State for Scotland for over 25 years – told the Sunday Times in July that the UK government’s figures for future oil revenues were wildly understated, not a single other newspaper picked up the story.

But the recent revelations are simply too big (and too many) to conceal. Oil rig workers have been telling their families of the magnitude of the finds as they get sent home on full pay to await the start of operations. Facilities in Shetland are so overburdened with new workers they’re having to be accommodated in huge floating hotels. And even the UK media can’t keep a secret that size.

Last year Alistair Darling bizarrely suggested that the oil might run out as soon as January 2017. And as recently as this month, the Secretary of State for Portsmouth was attempting to hold the line by rubbishing as a mad nationalist conspiracy theory the idea that a new oil bonanza was just over the horizon.

It seems unlikely to be a tenable position for the next four weeks. It remains to be seen whether the people of Scotland will swallow the same lie twice, and once again vote to hand an almost unimaginable amount of Scottish wealth over to London and trust that it will be spent wisely.