KEITH ISAAC accuses Vince Cable of having undersold shares in the Royal Mail privatisation, thereby denying him and all other British taxpayers “billions of pounds of revenue” (Letters, August 9).

This, he says, is “true historical fact”. Well the first part is true but only insofar as this was a judgement based on assessment of the risk of overpricing and the sale falling through.

An independent report concluded that it would have been safe to sell at a slightly higher price but that the difference in outcome would have been negligible.

The sale raised £2 billion for the public coffers – Mr Isaac may feel he’s been short changed but there is no evidence to suggest this was the case.

At least Sir Vince had a plan for the sale of Royal Mail and there was broad consensus that it was a success.

Contrast with Brexit, for which the government does not appear to have any plan and negotiations have stalled at the first hurdle.

Mr Isaac accuses Sir Vince of scaremongering and says that he speaks “without proof”.

Of course you cannot prove definitively that anything will happen in the future; you can however use past experience to assess the balance of probability.

There is little cause for optimism about Brexit, especially if we leave the single market and customs union.

Our economy has already taken a hit this year and, unless the Brexiteers in the government sharpen up their act very soon, things can only get worse.

Vince Cable has proven remarkably prescient on economic matters in the past. He may yet do so again.

Richard Brown, Copmanthorpe, York