On Friday 5 December 1952 a poisonous smog settled over London's streets. By the time the darkness lifted a few days later over 4,000 people had died in what is still officially the world's worst air pollution disaster. In the aftermath of the episode there was a public clamour for action, but it wasn't until the 1956 Clean Air Act that the problem was adequately addressed, the result of which was an increase in December sunshine in the capital by 70%.
Today, London's air still looks clean, but do not be fooled: it is both toxic and illegal. This time around however, the problem comes not from coal-fired manufacturing but from invisible gases such as nitrogen dioxide (No2) and particulate matter (PM2) which are largely produced by cars, buses and vans. These gasses are linked to increased incidence of bronchitis, asthma, strokes, cancer and heart disease. Indeed, the problem is now so severe that air pollution ranks above alco-hol consumption or obesity in terms of its impact on the health of Londoners, causing equivalent to 9400 deaths a year.
Enter Sadiq Khan, the new Mayor of London, who last week used his honeymoon period to announce that he will be consulting on the introduction of a new Clean Air Zone (CAZ): a charge on polluting cars entering central London and the expansion of the Ultra Low Emissions Zone (ULEZ) across the whole of inner London by 2019 (something recommended by IPPR's recent Global Green City report). If the details are as bold as the headline this new CAZ will ultimately see all but the most efficient diesels pushed off London's roads and catalyse a shift towards electric vehicles as well as walking, cycling and public transport.
Khan's plans are both radical and brave. They far exceed the ambitions of existing plans set out under Boris Johnson, which would have seen London's emissions remain illegally high for well over a decade. But, announcing the policy will probably prove to be the easiest part of the process. The new mayor now has a fight on his hands to gain support for it - just ask local leaders who attempted and failed to introduce similar charges in Manchester and Edinburgh. In particular, he will face op-position from people on low and middle incomes who cannot afford to change their car in order to avoid the charge and small businesses who will fear its impact on their profit margins.
If he's smart, the mayor will pre-empt the concerns of both groups before the consultation begins. This will mean lobbying government for a new scrappage scheme for older diesel cars as was trailed as part of his announcement on Friday, but may also include temporarily discounting public transport for people on low incomes; finding some way of softening the blow for small businesses (either through delaying the compliance date or through a temporary business rates reduction); and investing now in improved public transport in the outskirts of London. All this won't come cheap: if Khan was hoping to use the revenue from this policy to fund his proposed fares freeze he may need to reconsider.
However, just as important as 'buying off' those groups who stand to lose out from the introduction of the CAZ, will be communicating why everyone benefits from its introduction. London is in the midst of nothing short of a health crisis. Over 2,000 schools are within 400 metres of roads carrying more than 10,000 people per day - we are quite literally poisoning our children. The cost to the NHS is likely to run into the hundreds of millions, if not billions. And yet all the time, the number of cars on London's roads continues to climb. Only a radical solution of the kind set out by the Mayor on Friday will ensure London is cleaner, healthier and safer in the years to come.
Harry Quilter-Pinner leads the health programme at IPPR, the UK's leading progressive think tank, and co-authored London: A Global Green City which proposed the introduction of a Clean Air Zone in London, as announced by the Mayor of London on Friday.