Will Boris Johnson run again or Seb Coe sprinkle Olympic stardust on the mayoralty? Maybe Tessa Jowell or Diane Abbott or the noble Lord Adonis? Labour’s glitterati form a queue. Two-and-a-half years away from the next election for the London mayor we should focus on the big ideas, not the big names. Ideas excite, energise and engage beyond the already committed. They are the foundations of a mass party and they change lives, surely the real purpose of politics.

The Conservatives experimented with primaries last time and Labour is promising them now. They offer an unprecedented opportunity for a different kind of politics.

The London mayor holds the UK’s biggest directly elected mandate. We should expect an ambition that matches the scale of the opportunity. It should be bold and deep-rooted and, above all, it should be ours, not marketed to voters with badges and balloons in the four short weeks of an election campaign but imagined and owned by us all. Do that well, politicians note, and the poll takes care of itself.

More than 8 million people live in London, alongside some of the world’s most successful organisations. It is, in many ways, a rich and gifted city but not always a happy, healthy or productive one. More than a third of its citizens fear crime on the streets, 28% are in poverty, and the richest can expect to live 20 years longer than the poorest.

Consider the options. What if, for instance, the mayor, its businesses, public services, charities and citizens determined to make London the greatest place on Earth to raise a child? Attacking child poverty would have to be a priority; employers would need to step up, as 600,000 workers in the capital are paid below the living wage. A London child trust fund – modelled on San Francisco’s or the cancelled UK scheme – could give every newborn Londoner a bank account and a £100 deposit, enabling parents to save for their children’s future.

Streets account for 80% of our public spaces but don’t feel very public to our children. Perhaps a quarter could be designated play streets, free from traffic at the weekend, reclaiming them for the social interaction and outdoor play that has almost entirely disappeared from many neighbourhoods.

Tourists complain that London is not child-friendly. What could our restaurants, our transport system, our tourist destinations do to change that? Ideas tumble out when you begin to talk about the possibilities.

Alternatively, could London become the best place to grow old, the global capital for ethical business, or the world’s most peaceful city, free from hatred and violence on our streets and in homes? The list goes on.

This isn’t only about the mayor’s direct responsibilities – transport, policing or housing, important though they are. Even more can be done with the powers of influence – the voice, the visibility and the capacity to convene. These are the superpowers of the mayoralty overlooked by policy brewed in Westminster and ignored in a sham public discourse that fixes on political celebrity.

It can be done. Mayors across the world have rocked their cities in recent years with comparable achievements and the range is thrilling. San Antonio’s mayor ran huge live events for thousands of citizens to decide the city’s budget. Bogota’s former mayor, Antanas Mockus, asked its citizens to voluntarily pay 10% extra tax and 63,000 did (perhaps that could fund the London child trust fund). He halved traffic deaths by painting the street where people died and employing 400 mime artists to illustrate the dangers of jay-walking. Oklahoma’s mayor transformed his city’s waistline by personally fronting a campaign to “lose a million pounds”. And Helsinki has its youth guarantee of a job, study or training place for every young person.

If they did it, so could we. Changing London is a website launched today to debate ideas from London’s citizens and friends. Street-based activities will widen engagement. After six months, we will pull the ideas together and use them to sharpen the ambitions of the next mayor. Please join the conversation.

Martin Luther King famously believed that change wouldn’t come overnight but that we should always work as though it were a possibility in the morning. A website and a road show won’t deliver that change but ideas light the fuse. Share yours. Rock this city.