Big Society Capital, a social impact investment firm in London, is a globally unique organisation, set up in 2012 to be a champion of social impact investment and an impact investor itself. Big Society Capital is the first organisation of its kind, established to develop a sustainable social impact investment market in the UK so that charities and social enterprises can grow their positive impact on society and continue improving the lives of vulnerable and disadvantaged people in the UK. In its first 6 years, together with its co-investors, Big Society Capital has helped over £1bn of capital reach over 1000 different charities and social enterprises. It has also played a major role in improving the enterprise, investor and policy environment in which social impact investments are made. Big Society Capital’s task is still just beginning, however, and the next few years will see opportunities to build on what has been achieved so far, to grow the use of social impact investment in the areas where it can work most effectively, to make it as relevant as possible to social organisations, charities and social enterprises, and most importantly of all, to measure and scale the positive social impact created through impact investment.