Michael McCarthy: Huhne's departure will sadden all who care about the environment

His brilliant brain was never put to better use than when he saved the day at the Cancun talks

With the enforced departure of Chris Huhne the environment in Britain has lost its most intelligent and powerful defender. In his 20 months at the Department of Energy and Climate Change, the MP for Eastleigh has shown not only a masterful grasp of policy, but a willingness to fight his corner in the Cabinet for the green causes he has long championed.

In particular he has stood up to the Chancellor, George Osborne, and to Mr Osborne's intensifying attack on environmental concerns as an irrelevant side issue which only harms economic growth.

After the Chancellor's discourse to last October's Conservative conference, in which he roused the party faithful by crying "We're not going to save the planet by putting our country out of business!", Mr Huhne responded by echoing Mr Osborne's own words back to him, asserting: "We are not going to save our economy by turning our back on renewable energy."

It did not make him popular with his Tory cabinet colleagues – indeed, it made him hated by some, who will privately cheer his fall – but it did reassure all who care about the environment that their concerns were being upheld at the highest level.

Strange that it should be Mr Huhne taking this role, a former financier and financial journalist (he was once City editor of The Independent) who, let it be said, is a rich man with a portfolio of properties, but who could have devoted his whole life to money making and raked in millions.

He could have bought a flash country estate and taken up huntin', shootin' and fishin' like many an upwardly mobile hedge-fund boss of his generation. Instead, after a visit to Africa, he conceived a passion for environmental and developmental causes and went into politics full time for the Liberal Democrats.

His rise has been helped by what even his enemies acknowledge is a brilliant brain. "You should see him in negotiations with the Treasury," a Tory colleague once murmured in admiration. "But then, he was a ratings analyst."

This intellectual agility was never put to better use than at the Cancun climate conference in December 2010, when the laboriously constructed negotiating process appeared to be in ruins after the disastrous Copenhagen talks of the previous year.

Cancun was meant to repair the process so that the world could continue to grapple with the global-warming threat, but it too appeared to be heading for deadlock over the current emissions-cutting treaty, the Kyoto protocol: South American countries insisted on renewal, but the Japanese said Never.

Mr Huhne was put in charge of a committee to try to bridge the divide, which he proceeded to do by producing a text of such subtlety that even the opposing sides felt able to agree to it, and the process was saved.

It might seem an obscure victory – but it was a crucial one for the future. There is no doubt that Mr Huhne, as was said of Othello, hath done the state some service. He has been a genuine big beast in the political jungle, and to see him brought low is very sad. His departure is also a very great loss to anyone who cares about the environment and the green economy – especially in an administration which proclaimed it would be the greenest government ever, but which looks a paler shade of green with every day that passes.