This book reflects on work done through the Managing Extreme Technological Risk (METR) project, a pioneering research programme within the Centre for the Study of Existential Risk, University of Cambridge. METR has been both an exercise in 'academic engineering' to address major global challenges, and a research programme that extends beyond traditional academic outputs into methodological development and innovative forms of expert engagement and outreach.Managing Extreme Technological Risk explores how the METR programme developed a model that is needed to effectively understand risks to the survival of humanity, as well as their management and mitigation. It reflects on the challenges faced and lessons learned in the process of building a research community focused on this aim. This book brings together findings and future considerations from a key formative phase, not just for the Centre, but for the field of existential risk and aligned areas of research as a whole. It relates the story of this journey and outlines some of the programme's specific findings. There is an overall focus on what has been learnt for approaching the study of existential risk and how this can, and must, be taken forward by others, urgently and at scale.