'Salmond hit by oil bombshell - economic policy in ruins." We've become used to the front pages leading day by day with "New blow for Salmond over EU, currency, deficit, oil (delete as applicable)".

Now, as we get nearer to the referendum date, the blows are turning into bombshells.

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As Alex Salmond prepares for the second televised encounter with his bete noir, Alistair Darling, the heavy artillery has been rolled out. The oil analyst and billionaire, Sir Ian Wood, has warned Scots that the Scottish Government's forecasts on North Sea oil revenues are "grossly exaggerated". The oil is running out, he said. Our children should know this.

Actually, I don't think anyone is in any doubt that the oil will run out - Unionist politicians and the Office for Budget Responsibility have been saying so very loudly for the last two years. But there's still around 35 years of it left which isn't exactly the day after tomorrow. Everyone accepts the estimate by Oil & Gas UK that there is up to 24 billion barrels of oil still there under the North Sea, even if not all of it can be extracted at a profit.

Recoverable reserves of oil and gas could be worth £200 billion to the economy over the next 20 years - a tidy sum. And who made that forecast? Well, it was the same Sir Ian Wood in his industry-wide report published in February. Look it up, anyone can. David Cameron endorsed it personally in Aberdeen. But Sir Ian, poor chap, seems to have had an optimism bypass just in time for the second Great Debate.

You can already see Alistair Darling jabbing that finger at Alex Salmond and demanding: "What is your Plan B for when the oil runs out?" The truth is no-one knows exactly how much oil can come out the North Sea before 2050 and we are all in the realm of speculation. Even the "other" oil economist, Professor Sir Donald Mackay, who says there is a "mountain of black gold" still under the North Sea. All we know is that most countries in the world would give their eye teeth to have the "burden" of £1-£1.5 trillion in oil reserves.

Speaking personally, I'd be quite happy for a lot of it to remain under the North Sea. The dash to extract every drop of oil and gas is unseemly and environmentally unsound. What we should be talking about is how quickly Scotland's abundant renewable energy can be tapped. Last week the Scottish Government announced that work will begin next year in the Pentland Firth on one of the world's largest tidal energy projects. We have 25% of Europe's offshore wind potential - but with the relentless focus on oil, oil, oil I fear we are missing the point: hydrocarbons are on their way out.

Mind you, no-one can say exactly how soon renewables will take over from fossil fuels - only that they will. Nor can anyone say exactly how Scots will access BBC television channels after independence. Though there is little doubt that Scots will be able to watch them - assuming they still want to - as viewers can in Ireland. The BBC's UK channels are all listed in the daily newspapers in the Republic and are available on Sky, cable and free to air Freesat.

But this didn't prevent Lord Birt, the former BBC Director General, firing a broadside at the Scottish Government for its "make-believe" proposal in the White Paper for a joint enterprise post-independence between the BBC and a Scottish Broadcasting Corporation. Ain't gonna happen. Don't even think about it. This allowed various media outlets to recycle their "No Strictly after Indy" headlines from last year. "Will independence kill off Balamory?" asked one, even though Balamory was killed off several years ago.

Cue another question tomorrow night from Alistair Darling: "What is your Plan B for broadcasting. You can't have the BBC so what will you have? White Heather Club television?" The FM will reply that an SBC will be able buy in all the David Attenborough series it needs, but since none of this has actually been negotiated he can't say for certain. It is theoretically possible that the BBC could, out of spite, try to block its programmes or try to charge excessive prices for them, though it is most unlikely. The BBC will almost certainly want to retain its branding over the British mainland, as it has in Ireland, and would want to ensure that its services were at the very least available bundled with other services and a Scottish version of Freeview.

The other big issue tomorrow night will be the National Health Service and the Yes campaign's claim that it is under threat from privatisation. Alex Salmond's second Declaration of Arbroath last week promised that a publicly funded and publicly provided National Health Service would be a bulwark of the constitution of an independent Scotland. But is it really under threat? The former Labour health minister, Malcolm Chisholm, says that the SNP is spreading lies. Since health is devolved, there is no way the NHS can be subjected to the market reforms in England while the Scottish Parliament retains control.

However, as the health service union Unison pointed out last week, it would be naïve to believe that the Scottish service could remain totally immune to what is happening in the south - the invasion of private provision on a massive scale. The objective of the UK Government is to reduce the proportion of state funding of the NHS as private firms take over, and this will eventually be reflected in the Barnett Formula - assuming it still exists. In the longer term there could also be legal pressure from private providers to gain access to the Scottish NHS under new competition rules, if Scotland remains in the UK.

But Salmond will have to be careful what he says here, for there is no immediate danger to the Scottish NHS, which is well funded and protected by the Scottish Parliament. He risks being accused of a Yes version of Project Fear. Mind you, since the No campaign has suggested - without foundation - that Scots might not get treatment in English hospitals after independence, this would be a pretty blatant case of pots and kettles.

Of course, tomorrow's encounter would not be complete without another dialogue of the deaf over the currency. Darling will say that the UK parties have ruled out a common currency after independence; Alex Salmond will say they aren't serious. At the Edinburgh Book Festival tomorrow I will be interviewing the Nobel Prize-winning economist, Joseph Stiglitz, who was on the Scottish Government's Fiscal Commission and has views on this. He says that the present UK Government's rejection of a single currency is purely a "negotiating position" and that if there is a Yes vote there will certainly be a common sterling zone. Others, like the bank HSBC, say different.

You pays your money. There is ultimately no answer to this question either, since the UK Government has ruled out any "pre-negotiation". Instead George Osborne issued a unilateral declaration of monetary exclusion. Ed Miliband has even promised to rule out a common currency in the next Labour manifesto - silly man.

But there is some question about exactly how much impact this currency stuff is really having on Scottish voters. Westminster's threatening posture may have made many Scots think twice about voting Yes because of their pensions and mortgages. But the polling evidence since the last Darling-Salmond encounter suggests that that a lot of voters still don't believe the threat is genuine. The Yes campaign has been intensively canvassing in working-class areas of Scotland and getting what they claim are very positive results.

As I heard more than one person remark last week: "Do poor people in Scotland really care about whose head should be on the money they haven't got?"