This radio piece highlights ClientEarth—one of the most active organizations fighting for clean air in London. With offices across the world, the nonprofit law firm has fought the coal industry, petroleum giants, and polluting corporations. In its battle against the British Government, it has proven to be a formidable foe in court. But ClientEarth's work is far from over. While air quality continues to worsen in London, the question remains whether ClientEarth has met its match. Will it be the final arbiter, or will it flounder?