When Sadiq Khan announced that he was intending to be the greenest mayor ever, environmentalists across London felt a little shiver of déjà vu. 'I want to be the greenest thing ever' is on the way to becoming the environmental version of 'my client is a legitimate businessman' - not something which inspires a huge amount of trust.
But while Cameron blew it, Khan is in with a chance. This week Khan will face up to his first questions from the Greater London Authority (GLA). It will be his first big effort to live up to his 'greenest ever' aspirations. And his proposals, for a new Ultra Low Emission Zone (ULEZ) to reduce traffic pollution and clean up the city's appalling air quality, look really good.
It's still early days, we don't even have all the details of the consultation process yet, but Khan is calling for a bigger, tougher and earlier ULEZ. It will extend the zone from the North Circular to the South, adding an extra charge for central London, and, hopefully, introduced well before 2020.
People, and particularly business, are always a bit resistant to change, let alone change brought in by regulation. As with the previous ULEZ, and the congestion charge, and most other attempts to limit pollution, there will be claims that the costs are too high, it will unfairly penalise people reliant on old, dirty technology, and the economy will suffer. Khan has made some attempt to deal with these issues, supporting a diesel scrappage scheme to help those stuck with a dirty old vehicle, and leading from the front with buses expected to be clean before private vehicles.
Creating a rapidly expanding market for cleaner vehicles and transport systems - public, private and commercial - will make it easier for other cities around Britain and the world to improve their air quality. It will also give us a head start in the global electrification of transport needed to preserve our climate. And we all know the urgency. Right now Londoners are, collectively, forcing our children to, in effect, chain smoke.
The key thing to remember when listening to the inevitable calls for weakening or delaying action is that Khan's proposals only look radical in the context of decades of inaction. London's air was initially supposed to meet EU standards by 2010. A whole series of postponed deadlines and ineffective policy responses has left us in the toxic soup where we now stew. The date for compliance is now estimated to be 2025. Like most heavy smokers, we know what we need to do but we'd rather not do it now.
And the sad fact is, even if they are fully implemented on schedule, Khan's plans will probably not be enough to get London's air quality up to the legal standard, particularly with extra emissions from any airport expansion. But while they should make a big dent in the air pollution death toll, they will not, by themselves, be enough to make London's air genuinely safe to breathe.
There are strong arguments to do more, but the ones we are likely to hear will favour doing less, and allegations of insupportable costs will be flung around the GLA assembly chamber as though Khan was arguing for Brexit. Here are two more to add to your collection.
Firstly, the Royal College of Physicians claims that 'the health problems resulting from exposure to air pollution have a high cost to people who suffer from illness and premature death, to our health services and to business. In the UK, these costs add up to more than £20 billion every year.'
And secondly, for every person killed in London by a traffic accident, nearly a hundred are killed by low air quality.
Imagine if that was reversed, if London's traffic was killing ten thousand people a year through collisions, would we still accept it as the price of urban living? How many thousands of deaths would we tolerate if we could see them happening on our streets?