Keith Johnstone entered the Royal Court Theatre as a new playwright in 1956: a decade later he emerged as a groundbreaking director and teacher of improvisation. His decisive book Impro (1979), described Johnstone's unique system of training: weaving together theories and techniques to encourage spontaneous, collaborative creation using the intuition and imagination of the actors. Johnstone has since become world-renowned, inspiring theatre greats and beginners alike; and his work continues to influence practice within and beyond the traditional theatre. Theresa Robbins Dudeck is the first author to rigorously examine Johnstone's life and career using a combination of archival documents – many from Johnstone's personal collection – participant observation, and interviews with Johnstone, his colleagues and former students. Keith Johnstone: A Critical Biography is a fascinating journey through the physical spaces that have served as Johnstone's transformative classrooms, and into the conceptual spaces which inform his radical pedagogy and approach to artistic work.