The Fourth Doctor, assisted by his leather clad barbarian warrior companion Leela, as played by Louise Jameson, journeyed to a mining ship on a desert planet run by a robot labour force in this 1977 adventure, and this one really is a bonafide classic. Often cited as one of the best Doctor Who stories of all time for its excellent writing, superb direction and all round great performances, the third episode of this four part escapade peaked at 13.1 million viewers when it aired on 12th February 1977. One of the very best of the Philip Hinchcliffe era.