On January 5, with 360 days of 2017 to go, London's streets had already begun breaching their annual air pollution limits. Though the pea-souper smogs of the early 20th century are confined to history, invisible pollutants now permeate the air that Londoners breathe. And they're killers.
To save lives, but also to put London at the forefront of a clean vehicle revolution and spare its air pollution shame, the Mayor of London needs to introduce a ban on the dirtiest vehicles being used in the capital.
The way air pollution is measured and regulated in our cities is complicated. The rule, set in Brussels, is that no single location can exceed specific high concentration levels of pollutants more than 18 times in one year. Brixton Road in South London had bust through this limit 19 times by the night of the 5th January, and by the middle of the 6th, had exceeded the limit 24 times.
Back in the 1950s, most of London's air pollution came from burning coal for heating and industry. Now, a big bulk of the limits-busting pollution comes from vehicles and the worst culprits are diesel engines; there are more of these on the UK's streets than ever before. It's ironic, then, that news of London's transgressions have emerged only one day after scientists in Canada reported a link between an increased risk of dementia and living close to a busy road.
We already know that around 10,000 Londoners die prematurely every year due to the poor quality of the capital's air. The pollutants that are emitted by vehicles - but especially diesels - are a known cause of lung cancer and are linked to heart disease, stroke, premature births and impaired development in children. Our cars, vans and buses are pumping out invisible, toxic gases that are killing us and harming our future.
Who would tolerate such a state of affairs?
Paris, Madrid, Athens and even Mexico City all have plans to cut air pollution that include phasing out the use of diesel engines. London's Mayor Sadiq Khan has published a plan to reduce air pollution. But he has as yet fallen short of a concrete proposal with a clear phase out date to get diesel engines off London's roads.
Friends of the Earth, joined by a growing number of people in London and other UK cities, are calling for diesel to be banned by 2025, giving sufficient time for motorists and companies to change their vehicles. We owe it to our children and grandparents - and ourselves - to do this as a first step towards cutting the number of deaths and illnesses caused by air pollution.
Saving lives is reason enough but banning diesel could revolutionise transport in London, putting the capital in the driving seat of global vehicle innovation
Of course, you would not expect a green campaigner from a green charity to write about transport and not stress that we would all be better off - and so would the planet - if we took far fewer journeys by car and more by public transport, bicycle and on foot. We need a transport policy that helps people leave their cars at home. But motor vehicles are not going to go away, and therein lies the opportunity for London.
Without a shadow of a doubt, the London Congestion Charge, as well as regulation in Scandinavia, helped trigger the development of the petrol hybrid. Toyota's Prius was largely developed for cities that both regulated on carbon emissions for climate reasons but also on pollutants that directly harmed people's health. You cannot now travel more than 100 yards in central London without seeing a Prius.
Of course, the politics of monkeying with what people can and cannot drive, are notoriously sticky. But Ken Livingstone, Khan's Labour Mayoral predecessor, calculated that more people would be largely unaffected by the Congestion Charge than would be angered. And he's been proven right
London has the fifth largest metropolitan economy in the world. It is an economic titan that can change the course of history. And it is no exaggeration to say that a clear, phased outlawing of diesel, alongside incentives for people to get rid of their vehicles sooner than they may otherwise have done and the encouragement of clean alternatives, could transform the city.
New technologies, such as increasingly desirable electric vehicles, need big markets to help them deliver at scale and bring down costs - as did the Prius - and where better than fashionable, tech-savvy, congested, polluted London.
Of course, not everyone in London has the sort of income that will run to a BMW i3 or a Tesla Model S. To compensate for the negative incentive of the congestion charge, Livingstone packed the streets with buses and charged £1 for any journey anywhere.
Ironically, most London buses are still diesel. A really massive win would be to bring clean, mass transit to London's legions of bus users; and Khan could perhaps get one over on his immediate predecessor Boris Johnson's not altogether perfectly clean rehash of the Routemaster.
Bike lanes and pedestrian areas must also be prioritised; squeezing traffic of any sort out of London's high streets will make the city a pleasanter place. And above all, as Mayor Khan is wont to say, London must be a city for all Londoners.
But the capital's place in the world, its image and desirability will all be harmed unless the scandal of air pollution is not tackled fast. And where better to start than with a ban on the dirtiest of vehicles. It will save lives and improve quality of life, but may also help secure London's place in the future of travel. And that would be an achievement any Mayor could be proud of.