Energy tycoons in lobbying war over zonal pricing policy

Greg Jackson is fighting a battle but you would not know it. The Octopus Energy boss reclines at the back of a red bus emblazoned with his company's branding, midway through his annual "tech fest" event in Battersea Park, south London. Stephen Fry, Prof Brian Cox and Al Gore have all made appearances - a testament to Jackson's convening power.

- Alex Daniel

In the energy world, however, he cuts an increasingly divisive figure for backing zonal pricing, a scheme that would carve Britain up into different energy price regions. The policy could save consumers £3.7bn a year by making the power grid more efficient. "It is the single most important thing we can do to drive bills down," Jackson said.

But it has also sparked a ferocious lobbying blitz that has pitted him against Labour mega donor and fellow energy tycoon Dale Vince. A flurry of newspaper op-eds, paid-for research and off-the-record briefings ensued this year. One industry executive called it "the most vicious policy fight I can remember in energy... I have fallen out with friends."

By April, the debate had grown so heated that Jonathan Brearley, chief executive of regulator Ofgem, called for calm - a rare intervention.