About a month ago, I visited the aero engine factory of Rolls-Royce, in Derby. I was hugely impressed. Making jet engines able to work at extreme temperatures is an extraordinary achievement. Why does the financial industry not work this way? How might we bring the performance of finance close to that of other sophisticated businesses?

This is, in its essence, the question Mervyn King, governor of the Bank of England, was addressing in his controversial speech this week. His answer: break up the banks into “utilities” and “casinos” The former would be safe. The latter would live and die in the market.