Just like the euro, the debate over stamp duty is one of politics and not economics. Intellectually, the arguments that the abolition of this tax will benefit all those concerned, other than the Treasury, are irrefutable. And even the Treasury is said to accept privately that abolishing the 0.5% tax on share trading in the UK will reduce the cost of capital and boost trading, helping UK corporates and pensioners alike.

But economic rationale is not the issue, and Don Cruickshank, chairman of the London Stock Exchange and an extreme left-winger in his youth, should know this. That's what makes his latest broadside against the Treasury so interesting and, at the same time, so curious.