New Radicals 2016: how to make a positive impact

Every two years, the Observer and the innovation charity Nesta recognises 50 trailblazers who work for the public good. Here we launch this year’s competition – and catch up with previous winners
• Submit your nomination for New Radicals 2016 here
• Read about 2014’s new radicals
Four years ago, the Observer and Nesta, the charity that promotes innovation in society, jointly launched a hunt for Britain’s 50 new radicals – people, projects and organisations