but she falls unconscious. The Doctor, enraged, attacks Styre, but the Sontaran easily fends him off. Styre shoots him unconscious (believing it to be fatal) when he runs away. The robot, having captured the three remaining spacemen, brings them to Styre's ship, where it is revealed that Vural had tried to make a deal with Styre in exchange for his own life. However, Styre intends to experiment on Vural anyway. The Doctor recovers, disables the robot, and meets Sarah and Harry. He confronts Styre, goading him into a hand-to-hand combat. While they fight, Sarah and Harry free the astronauts, and then Harry climbs towards Styre's ship to sabotage it. Styre almost wins the fight, but Vural attacks him, saving the Doctor at the cost of his own life. Styre, now low on energy, heads back towards his ship to recharge, but the sabotage causes it to kill him. The Doctor informs the Marshal that not only has Styre's mission failed, but that the invasion plans are in human hands. This is enough to ward off the invasion, and the three can return to Nerva, or so they think. Production Working titles for this story included The Destructors. These two episodes were initially part of a six-episode arc, but Philip Hinchcliffe made the decision to split the arc into the four-part Ark in Space and this two-part story, sharing the same director and budget. To save money, Hinchcliffe decided that Ark would be entirely filmed in the studio and this story would be entirely filmed on location. He also settled on the Sontarans because they could re-use the Sontaran costume from The Time Warrior and therefore save the expense of designing a new alien. This was the first two-part serial to be broadcast since 1965's The Rescue and the last until 1982's Black Orchid. Although the serial was the third to feature Baker, it was actually the second shot, hence the out-of-sequence production code. This was only the second serial in the history of Doctor Who (the first being 1970's Spearhead from Space) to be shot entirely on location, in this case at Hound Tor on Dartmoor. However, unlike Spearhead from Space and the location material for other serials, the production was mounted entirely on videotape using early portable video equipment, rather than on the usual 16mm film. This use of location video was remarkable for the time, but technical problems