Jack Fenwick explores how the think tanks and pressure groups behind the black door of an anonymous building in Westminster have shaped the last decade of British politics - and asks how they might shape the next few years. For this programme Jack has spoken to more than 50 current and former government insiders about how the organisations based at 55 Tufton Street have influenced British public life. He reveals how organisations including the Taxpayers Alliance, Brexit Central and the Global Warming Policy Foundation helped set the narrative on issues such as austerity, Brexit and climate change. He tracks how some of their ideas become government policy, explores the issue of whether the rules governing these organisations need to change and, with a new Prime Minister in Number 10, he asks how the ideas developed behind one black door might influence policy behind the most famous black door in Britain. Producer and presenter: Jack Fenwick Assistant producer: Maddy Trimmer.