Bottom of barrel

Sam McComb (Letters, 8 July) is adamant that rUK would do a deal on a currency union ­because the oil revenues are critical to its economy. Holyrood’s hoped-for figure for oil revenues was £10 billion in its 2013 Scotland’s Balance Sheet estimates, but the actual value was well down on that: forecast by experts to stay in the £3bn-4bn per annum range, possibly even lower.

The £12bn-24bn always quoted as still waiting to be pumped up could give a further two or three decades of fair yield, but at ever-increasing cost per barrel, so there can be no expectations of additional revenues.

The UK economy is thus not critically dependent on the oil receipts, although the whole oil/gas endeavour contributes a moderate percentage to GDP. There seems no need for rUK to have to take on the risky role of lender of last resort for Scotland in a formal currency union just to keep oil monies coming in.

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For both Scotland and rUK, oil revenues will be slight after another 40 years, so permanent separation means they must be replaced from other sources – Holyrood has yet to spell out how.

Joe Darby