John Rentoul: Cameron's stand on Heathrow proves that his green agenda is not just a gimmick

Just before the 1997 election, Tony Blair was interviewed by three senior journalists from the Observer. When they had gone, he welcomed his next appointment by saying: "I've just had three guys in here telling me how to lose the election." Working for the most Labour-friendly of the quality Sunday newspapers, the three had naturally sought to encourage the Labour leader down a traditional Labour path and, being Blair, he had naturally turned down their offer so politely that they didn't notice.

I expect David Cameron is like that when left-of-centre columnists visit his Commons office, as he tries to persuade us – so far without success – to defect. Certainly, when I spoke to him recently, I invited him to prove that he meant what he said about the environment by coming out against a third runway at Heathrow. He hinted that he would shortly be taking up a more sceptical position. I went away thinking I would believe it when I saw it; he no doubt turned to his next meeting muttering about another journalist telling him how to lose the next election.

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I turned out to be wrong to be doubtful. Ten days ago, Cameron delivered a green speech in which he significantly toughened the Conservatives' opposition to a new runway at Heathrow. "There are now increasing grounds to believe that the economic case for a third runway is flawed," he said, "even without addressing the serious environmental concerns."

Cameron is quite right, of course, to go gently into the green stuff. There are not many votes to be had for a politician promising to return us to an agrarian society, as George Bush said when Blair was bending his ear about climate change. Cameron's speech was significant because we had good reasons for doubting his commitment. One is that he had fallen silent about green issues for some time, saying next to nothing about rising fuel prices; another, possibly related, reason is the imminent departure of Steve Hilton, one of his closest strategic advisers.

Hilton matters to the commentariat, because he is so closely attuned to its dominant ideology, a liberal, social-democratic green mush of the centre ground. But now he is off to California, because his wife, Rachel Whetstone, a former adviser to Michael Howard, has been appointed a vice president of Google. There were some unconvincing conversations at the time the move was announced about how Hilton would stay in touch by telephone, but the time difference is an obstacle and my understanding is that Cameron accepts that Hilton is unlikely to be coming back before the election.

So it was important that Cameron made such a strong statement of commitment to green politics. It helps dispel, even if it does not do so entirely, the notion that the number of "True Believers" in Cameronism is small and possibly does not include the leader himself. Cameronism being defined for these purposes as the belief that the strategic imperative for the Conservatives is to contradict all known preconceptions of the party. Green policies are central to that, and Cameron's speech last week was important because it was an emphatic rebuff to those in his party who said that the rise in oil prices were a chance to drop all the green window-dressing.

In a mirror-image of those traditional Labourites who thought that Blair, once he had established a commanding opinion-poll lead, could afford to ditch all the centrist sell-out stuff now that it had done its job of attracting former Tories to the fold, the Tory right now wants Cameron to drop all the nonsense – associated with Hilton – about "decontaminating the Tory brand". Hugging huskies and hoodies has done what we needed it to do, they say, now can we get back to being Tories again?

To which Cameron's answer was an unequivocal no. To his credit, he has used a huge opinion-poll lead to tell his party what large parts of it don't want to hear. Contradicting the idea that high fuel prices meant we can no longer afford action against climate change, he said: "We can't afford not to go green."

However, that still leaves a more fundamental question unresolved. Is green politics still a matter of positioning for Cameron, or is it one of substance? The argument the Tory leader is having with his party is over whether they still need to appear to be green, not over whether they would actually be green in government. Cameron's choice is harder than Blair's in 1997, because the "difficult choice" Blair had to make was to refuse to do things that were expected of him by the left. Cameron has to decide whether to go green in ways that sound fluffy and friendly to the commentariat, but which will produce fiscal winners and losers among the electorate.

Yesterday, Gordon Brown tried to make it look as if he were taking all the difficult decisions that Cameron had "ducked". On nuclear power, Brown may have a point, except that his decision in favour – taken jointly with Tony Blair in 2006 – is irrelevant in the short term. It certainly has nothing to do with the Planning Bill, voted on by MPs last night, because the first stage would be to replace existing nuclear power stations, which already have planning permission. You would have thought that, with oil prices having doubled in the past year, nuclear power might finally be economically viable without subsidy, but the future price remains uncertain.

But in the same breath as Brown condemned Cameron for ducking the choice on nuclear power that is needed to reduce dependence on oil, the Prime Minister condemned him for ducking the choice of airport expansion.

It would seem to me that coming out against a third runway at Heathrow – and opposing the Planning Bill – was a far harder and better choice than claiming credit for a decision in principle on nuclear power taken in conjunction with your predecessor. It simply is not credible to back airport expansion and to travel to Jeddah to urge the Arabs to pump more oil while at the same time saying, as Brown did in the Commons yesterday, that we need as a world to consume less oil in order to mitigate climate change.

Of course, opposing a new runway at Heathrow could be portrayed as the easy, negative, do-nothing option. But it takes quite a risk with organised capitalism – the CBI in particular. And it would in time have consequences for the price of flying, because the only sensible way to ration limited runway space would be by using the price mechanism.

As such, Cameron's stand on Heathrow is consistent with his policy of green taxes, which he stands by despite pressure to call for lower fuel duties. He has promised to return the revenue of such taxes to the taxpayer in tax cuts elsewhere, but the electoral viability of this remains to be tested.

As a policy platform, it has been electoral poison ever since the German SPD tried it in 1989. Only a politician who is 20 points ahead in the opinion polls could promise it. Only a politician who had established some real green credibility could deliver it.

j.rentoul@independent.co.uk

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