Is what investment banks do largely useless? Six years ago, Adair Turner, then chairman of the Financial Services Authority, provoked uproar in the City by suggesting that some of what went on in trading rooms in the run-up to the financial crisis was “socially useless”. (He subsequently conceded he should have said it was “economically” useless.)

Now Professor John Kay has gone further and argued that much of what the modern financial system does contributes little, if anything, to the betterment of lives and the efficiency of business.