Dramatised documentary in which Peter Ackroyd traces the effects of literature on historical movements, and examines how the ideas of 18th-century philosophers Denis Diderot and Jean-Jacques Rousseau played a part in the development of the French Revolution. The programme also explores their impact on British poets and writers, including William Blake, Samuel Taylor Coleridge and William Wordsworth. David Tennant, Dudley Sutton and David Threlfall star.