One quirk of the water industry in England and Wales, where customers are beholden to local private-sector monopolies, is the war dance that takes place every five years.

It runs thus. Companies tell regulator Ofwat the financial returns they want in order to keep the taps running, upgrade infrastructure over the next five years and make an acceptable profit — and how much bills will therefore need to rise. Tough talk, and threats about reducing investment in Britain, are the norm. Eventually the regulator publishes a final settlement.

This time, that war dance has proved sufficiently frightening that Ofwat on Thursday said water bills could rise by an average of 36 per cent for the five years from April 1. That’s more than it previously indicated, but less than the industry wanted. Still, it feels like a coup for investors. Shares in the handful of listed water companies traded up on Thursday morning.