n 1858 MPs sitting in the House of Commons were so overcome by the stench of the sewage-ridden Thames flowing past Parliament that they hung enormous vinegar-soaked sheets over the windows to ward off the smell long enough for everyone to vote. They quickly found £3m for an unprecedented overhaul of London’s sewer system. It has survived to this day.

That investment formed part of the late 19th Century transformation of London’s public infrastructure, motivated by a desire for the good health of the city and the recognition that this was a proper concern for government. Diseases like cholera were eradicated, life expectancy vastly improved and London’s environment was transformed. Those vinegar soaked sheets came down, never to be put back up. Public health solved, then?

Sadly not. We might have tamed the microbial threats to our safety but that simply revealed new challenges. Life for Londoners is healthier and safer than it was for our Victorian ancestors but London is not a healthy place to live even by the standards of our biggest city rivals around the world.

We have the highest rate of childhood obesity of any major city and more than half the adult population are obese or overweight. More than one million Londoners will experience mental ill health this year – the total economic and social costs are estimated at £26bn annually. And these issues disproportionately affect the poorest – those in some of the richest wards can leave a full 25 years longer than those in the poorest. London comes 7 out of 14 in health rankings of global cities.

In our fifth London Paper, released today, we ask: What would London look like if it was a healthy city; if it aimed, like doctors, to “first do no harm”?

Just as in the nineteenth century, we require ambitious investment in the fabric of the city and in our communities. The so-called ‘lifestyle’ diseases with which we have to grapple today – diabetes, heart disease, lung cancer, liver disease – are badly misnamed. Washing your hands and drinking clean water largely prevent cholera; yet nineteenth century leaders didn’t put advisory stickers on polluted water pumps; they built sewers, decent housing and public infrastructure to provide clean water. They didn’t just urge people to wash their hands; they removed the tax on soap. And to round up the laggards they introduced legislation to enforce sanitation standards on housing and public works. In the twenty first century we are quick to tell people what to do but much slower to tackle the underlying causes of poor health.

Healthy communities would be more equal, they would be friendly and supportive, with good quality houses. They would be easy and safe to walk and cycle around, and the air would be clean and safe to breath. They would be safe and peaceful places, free from harassment and the fear of crime. Healthy, cheap food would be easily available, and the sight of someone smoking would become increasingly rare.

Given the fairly limited formal powers of the mayoralty, it is surprising how many of these issues the mayor can directly influence: planning, transport, policing, air quality and more. Ideas – many drawn from elsewhere, particularly the recent London Health Commission – include banning fast food outlets near schools and smoking in public spaces like parks, enforcing strict new emissions targets, investing in cycling and walking and determinedly driving down car use, paying the living wage, and making the city safer particularly for women.

Alongside this we must tackle the stigma around mental health. Marion Janner described on Changing London her experience of navigating London with Borderline Personality Disorder; she recommended practical steps – training for tube staff and a more generic version of the ‘baby on board’ badge but concluded the best thing a new mayor could do would be to “speak openly and unsqueamishly about mental health”.

We could be better informed in other ways too. Traffic lights on restaurant food, as pioneered by New York’s former health-obsessed Mayor Bloomberg would help us make healthier choices. Knowing the signs and symptoms of cancer and the importance of screening could save your life. Knowing first aid could save someone else’s. We suggest bringing ideas like these together for a week each year where the mayor leads the city in a determined effort to learn the skills which will keep us healthy.

In health policy London punches below its weight; cities like New York have shown the way in recent years and have seen life expectancy rise dramatically. A transformation of the scale we need will require a generation to take hold but the leadership and the commitment are necessary now and much can be achieved even in a five year term. Nineteenth century boldness transformed the city; London’s next Mayor has the chance to do so again.

Changing London is hosting an open meeting with Bharat Mehta, Christian Wolmar, Sadiq Khan, Radika Bynon, Tessa Jowell, David Lammy, Rosie Ferguson and Oona King at the Abbey Centre in Westminster at 6.30 next Tuesday December 9th. It’s not a hustings, no big speeches, but a conversation begun. Register here