People are jaded of politics, angry with politicians, and increasingly doubt their power to make a difference. Yet every week an alliance of grass-roots organisations including churches, mosques and trade unions persuades employers to pay a living wage to their cleaners, creates a safe street, or wins legal status for an undocumented migrant. London Citizens translates the principles of Catholic social teaching into concrete victories -- not just in the justice it pursues, but in the way it pursues it: by building the power of civil society to hold decision-makers to account. Faithful Citizens shows how London Citizens puts into practice both the themes and methods of papal teaching on the common good, subsidiarity, solidarity and justice. Through interviews with its organisers and leaders, it shows how LondonCitizens' victories are achieved through the methods of community organising, first developed in the poor areas of Chicago in the 1940s and made famous by Barack Obama. Faithful Citizens argues that community organising and Catholic social teaching are made for each other - the 'fuel' of Church's teaching driving the 'vehicle' of community organising.