Rana Mitter explores why we sleep with pioneering researcher into the body clock, Russell Foster; Matt Berry, actor, comedian and writer who wrestles with insomnia; Brigitte Steger who has explored Japanese and other global sleeping cultures and Katharine Craik, a renaissance scholar whose new opera project for children is called Watching...back in the 16th century the watching hours were part of a segmented sleep pattern which only disappeared with the industrial revolution.