Across the globe, the so-called Big Four accounting and audit firms – Deloitte, PricewaterhouseCoopers, Ernst & Young, and KPMG – are massively influential. Together, they earn more than US$100 billion annually and employ almost one million people. In many profound ways, they have changed how we work, how we manage, how we invest and how we are governed. Stretching back centuries, their history is a fascinating story of wealth, power and luck. But today, the Big Four face an uncertain future – thanks to their push into China; their vulnerability to digital disruption and competition; and the hazards of providing traditional services in a new era of transparency. Both colourful and authoritative, this account of the past, present and likely future of the Big Four is essential reading for anyone perplexed or fascinated by professional services, working in the industry, or contemplating joining a professional services firm.