Serial: 4B  Episode Nos. 390 and 391.  Title: The Sontaran Experiment

The Doctor and his friends transmat to a supposedly uninhabited Earth, purified by the solar flares 10,000 years previously.
They are therefore quite surprised to find a small group of ragged hostile men, some of whom are subjects in callous tests of human physical limitations being carried out by a Sontaran warrior in preparation for an invasion of the entire galaxy...

starring Tom Baker as Doctor Who, Elisabeth Sladen as Sarah Jane Smith, and Ian Marter as Harry Sullivan. Written by Bob Baker and Dave Martin, Produced by Phillip Hinchcliffe, and Directed by Rodney Bennett.

Originally transmitted from 22 February 1975 to 1 March 1975 on BBC1.

DVD Features:

 - Graphical menus, episode selection, and scene selection features.

                        - Commentary track by actor Elisabeth Sladen (Sarah Jane Smith), producer Philip Hinchcliffe, and co-writer Bob Baker.

                        - Information Text with pop-up production subtitles that play throughout the story.

                        - Subtitles for the hearing impaired.

                        - “Built for War  A new 40-minute documentary about all of the Sontarans’ appearances throughout Doctor Who,

                                    featuring interviews with actors Elisabeth Sladen, Colin Baker (the Sixth Doctor), Nicola Bryant (Peri),

                                    script editors/writers Terrance Dicks, Anthony Read, and Eric Saward, writer Bob Baker, and stuntman

                                    Stuart Fell.

                        - Photo Gallery.  5 minutes of still photos taken during the production.

                        - This disc boots up with a new 30-second trailer for the Complete Second Series Box Set starring David Tennant.