The Haweswater reservoir in the Lake District is owned by United Utilities and supplies about 25 per cent of the water consumed by customers in the northwest

Under threat of nationalisation from a putative Jeremy Corbyn-led Labour government, Britain’s three listed water companies have agreed to the largest cuts in customer bills since privatisation by Margaret Thatcher 30 years ago.

The reductions will mean that households in the West Country will pay 15 per cent less at 2019 prices over the next five years. In the northwest of England, bills will fall by 11 per cent before inflation.

While the inflation link in water charges will mean bills will fall by less, new penalties for missing environmental and operational targets could mean suppliers having to cut household charges by even more as a means of compensating their communities.

Of the 17 water companies in England and Wales, three have made a fast-track