The stress test of London’s democracy must, surely, come with affordable housing, the city’s most pressing problem.

A new mayor demands 40% affordable housing in any new development but, as history shows, that figure is Mr Whippy soft.

Developers pull faces, scratch their heads, do the maths and it turns out their plan is not viable at 40%. How about 25% or 20% or 10%?

The Mayor and councils have a choice – dogma or expedience. Some homes or no homes. They cave. Democracies are timid and populist. Big development trumps small print.

At The City Is Ours, a new major exhibition at the Museum Of London exploring key issues of city life, including planning, transport, pollution and social cohesion, one exhibit displays a 360-degree view of parts of London in all its sprawling, disparate beauty and decay.

The City Is Ours, a new exhibition at the Museum of London

Through speakers, Londoners tell of their concerns. One little girl says, in a plaintive voice that should be singing nursery rhymes, that big companies will own everything in her future and the rich will own all the houses. So much for fairy castles and free unicorns.

London does not lend itself to the moral crusades of smaller cities like, for example, Copenhagen, which plans to become carbon neutral by 2025 or Medellin (pop 2.464million) where a free cable car system has transformed the drugs’n’murder capital of the world into a model for social cohesion.

What becomes evident, as the little girl’s dreamless commentary suggests and is evidenced in this exhibition, is that the two great powerful forces of the future live at the extremes of scale.

The City Is Ours, a new exhibition at the Museum of London

The first is corporate governance. Those faceless developers have a greater ability to shape the lives of many Londoners than a gaggle of politicians in City Hall – yet profit and monopolistic zeal, not the common good, is their guiding light. Is that sustainable?

In every realm, corporations, like the internet giants, have the sway and muscle to shape communities. Corporate governance could become the centre of gravity for political discourse and scrutiny in the coming years.

The second cluster of activity is the collective – bottom-up community action. Pocket-sized projects aimed at creating a better life for their participants.

Like food co-operatives. Consumers and farmers come together with a shopping list of produce; the consumers provide financial certainty for the farmers through subscriptions and, in return, receive deliveries of local produce.

In Todmorden, in the UK, volunteers plant mini-vegetable gardens wherever they can, sharing the result and binding a community blighted by post-industrial division.

The City Is Ours, a new exhibition at the Museum of London

There is a role for a democratic authority – as a facilitator, a mood-setter, a nudger, a strategist, a moral force – but increasingly the focus will shift away from the money-starved, inert institutions to the places where things actually can and do happen – in the boardroom and in the streets.

Director of the Museum of London Sharon Ament said: “In London, recent estimates predict that its population will grow to nearly 10million by 2024.

“In this age of the city, we’re asking – what does the future hold for these urban metropolises and how can we contribute to their sustainability and survival?”

The City Is Ours, FREE, Museum Of London , until Jan 2, 2018. The exhibition forms part of the City Now City Future season

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