Today Labour will set out how in government it would nationalise Britain’s energy networks — the cables and pipelines that deliver electricity and gas to homes and businesses. The party says that shareholders would be compensated, but not necessarily at market prices — because of deductions to take account of “asset stripping since privatisation”, state subsidies since the 1980s and pension fund deficits.

Last year National Grid’s CFO Andrew Bonfield told Financial Director that it would not be possible to nationalise the company without significant costs. “You can’t reduce bills and not cost the taxpayers anything and increase investment without someone somewhere paying something along the line.

“Effectively our increase in debt every year is greater than the dividend we pay, so the idea you can save the dividends and there will be this amount of money which will pay the interest costs of the government bonds you have to issue, and reduce customer bills, won’t work,” he said.