The problem of lethal air pollution though is far from limited to the capital with the problem linked to as many as 40,000 early deaths in Britain. Cities and major towns across the UK are now consistently breaching limits, resulting in a 'final warning' from EU regulators.
But just 30 miles from central London, a service station could be home to a solution. Next to the rows of petrol and diesel pumps at the busy Shell garage at Cobham services on the M25, a new stand dispensing hydrogen fuel sits alongside.
Hydrogen has long been touted as a potential aide to the energy transition - the journey from fossil fuels to low-carbon alternatives used for cars and trucks.
And Shell is betting big on hydrogen as part of its New Energies business, which aims to navigate the uncertain path from oil and gas to greener fuels.
"There is no single silver bullet. All of us would like a simple solution, there isn't one," Sinead Lynch, Shell UK country chair told The Huffington Post this week. "You can't pick winners, I'm not sure what the winner will be."
" There is no single silver bullet.
- Sinead Lynch, Shell UK
Yet the oil major, one of the world's biggest energy firms, has invested in the technology behind hydrogen - which uses a process of electrolysis to allow for production at pumps themselves, reducing the need for storage on site.
"You can store energy, use it for power generation, use it for fuel," Lynch said.
Fuel cells in vehicles generate power by using hydrogen in the tank and oxygen from the outside, with the only resulting emission being water vapour.
"Electrolytic Hydrogen is the cleanest and lowest-cost renewable fuel available for fuel cell electric vehicles," said Dr Graham Cooley, Chief Executive of ITM Power, a Sheffield-based business supplying the technology to Shell.
Shell isn't alone in betting on hydrogen. Toyota, Hyundai and BMW all have fuel cell cars which use the gas.
One hydrogen vehicle reaches 700km in range and re-fills in just five minutes.
The UK government has a target for 65 hydrogen fuel pumps across the nation by 2020 - perhaps low compared with Germany's 400 by 2023.
For now though, Shell plans to open three in the south east of England. "We're in a pre-commercial phase," Lynch said.
Yet for all its obvious benefits hydrogen carries one big drawback - the widespread perception it is perilously unsafe.
The fact hydrogen is explosive was proved with the doomed-Nazi blimp Hindenburg, which crashed to the ground in a fireball in front of assembled media in 1937.
The disaster claimed 36 lives and inspired a blockbuster Hollywood film, linking hydrogen and fatal fire in the minds of millions.
[HINDENBURG PHOTO HERE]
Yet today carmakers argue the explosive nature of the gas isn't dissimilar to that of petrol and diesel.
"I think it's just our perception of hydrogen being extremely flammable and dangerous compared to what we're comfortable with in this day and age, which is gasoline," a Toyota spokesperson told Computer World. "Gasoline is also an extremely flammable fuel, and one that does not escape like hydrogen."
Advances in technology have now made the gas a viable product on forecourts that are already used to selling flammable petrols and oils.
Hydrogen cars on the road
Toyota launched its Mirai hydrogen car in the UK in 2015, priced at around £66,000, and aimed at corporate and business customers.
The company last year said it was importing around 50 of the model into Britain.
Other brands with vehicles available include Honda's Clarity, Hyundai's ix35 and BMW's Hydrogen 7, though production availability and prices vary.
Hydrogen fuel cell cars are exempt from road tax and from the London congestion charge. But insurance can be hard to find. While less powerful cars generally attract lower premiums, not all insurers cover eco-friendly cars, according to Compare The Market.
But the perception of safety continues to be an issue for companies investing in the gas, and it's one Shell admits it is grappling with.
"Safety is the number on priority in everything we do," Lynch said. "Hydrogen is a mature industry. It is proven to be safe.
"But it's a different type of fuel and people need to get used to that. That's the part of this we need to really think about."
The speed at which companies and consumers make the switch to hydrogen will be crucial to solving the air pollution crisis.
And despite Shell's move into hydrogen in Britain, campaigners point out their efforts are a drop in the ocean.
Greenpeace UK's senior climate adviser Charlie Kronick said: "Moving away from polluting diesel cars is an absolute priority, but this token gesture is disappointing even by Shell's low standards."