The Androids of Tara ( TV story ) The Androids of Tara was the fourth story in season 16 of " Doctor Who " . It was part of the Key to Time story arc , and part one ' s broadcast occurred just days after the fifteenth anniversary of the show . It saw Mary Tamm take on four roles : Romana I , a doppelgänger of Romana in the form of Princess Strella , and their android doubles . The plot of " Tara " is a pastiche of . Several of the serial ' s working titles paid homage to this and many of the characters are based on their counterparts in the novel . Only with the BBC ' s interference was the potentially copyright - infringing name " Zenda " or " Zend " dropped from the title . Synopsis . Finding the fourth segment of the Key to Time was simple enough , but holding onto it may be another matter . The Doctor and Romana I find themselves embroiled in the political games of the planet Tara , where doubles , android or otherwise , complicate the coronation of Prince Reynart . Plot . Part 1 . The Doctor and Romana I arrive on the planet Tara in search of the fourth segment of the Key to Time and , for once , the quest is simple . While the Doctor goes fishing , Romana identifies and transforms the fourth segment alone . It was disguised as part of a statue . Her luck does not last , though . She is attacked by a Taran wood beast and only saved by the nobleman Count Grendel of Gracht . Grendel confiscates the segment as an unregistered mineral and insists the injured Romana accompanies him to his castle . Once there , it becomes apparent that Grendel believes she is an android . The swordsmen Zadek and Farrah have meanwhile recruited the Doctor to the party of Prince Reynart . The society of the planet Tara is a mix of the feudal and the futuristic , with a rigid social monarchical hierarchy developed alongside a skill in advanced electronics and android making , an ability endowed on the lesser orders . Centuries earlier , a plague wiped out nine tenths of the population . The workers , abandoned by the nobles at that time , began building androids to deal with labour shortages . The planet is now troubled by a struggle for the crown . Reynart is the rightful prince , but he is facing a challenge to his rule and coronation from his cousin , Count Grendel of Gracht . The Doctor agrees to help repair an android copy of the Prince . It is to be used to help him reach his throne and crown by diverting the attention of Grendel ' s men , while the real Prince slips into the coronation chamber through a back way . This plot looks plausible , but Grendel strikes first , drugging the Prince ' s retinue and kidnapping Reynart himself . Part 2 . When the Doctor and the swordsmen recover , they decide to change the original plan and crown the android Reynart instead . The party move through the tunnels beneath the royal castle to get to the throne room so that the facsimile Reynart can be crowned . If Reynart is not there at the correct moment , then he will lose his right to the throne ; Grendel may be chosen under the law to claim the crown instead . The real Reynart was wounded in his capture and has been imprisoned with Romana at Castle Gracht to prevent any legitimate succession . Romana learns that she is physically identical to another of Grendel ' s captives — the Princess Strella . By their elaborate ruse , the Doctor and his party succeed in getting the android Prince to the throne room , and the coronation begins . However , the android Prince is damaged , and it is clear the ruse will not hold for long . Strella enters the coronation room and pledges allegiance to the new King , but the Doctor suddenly rises up and with a shout of " No ! " strikes at her head with the King ' s staff . Part 3 . The Doctor has not killed Strella , but an android duplicate , who was programmed to kill Reynart . The oath taking is delayed while other possible androids are found , and the " King " is watched over by Zadek and Farrah . When he returns to Castle Gracht , Grendel is furious , but when he finds out that the Doctor and Romana know each other , he has his android maker Lamia , who is in love with him , make an android Romana programmed to kill the Doctor , the man he sees as the one who deprived him of the throne . K9 is enlisted from the TARDIS to provide armed support and scanning intelligence that confirms that the Count has the Prince , the Princess , and Romana in his castle . Shortly afterward , Till , Grendel ' s manservant , arrives at the Reynart estate and offers the Doctor a chance to collect Romana from the Pavilion of the Summer Winds , a nearby gazebo . It is , as ever , a trap . While this is happening , the real Romana escapes from Castle Gracht and heads off to find the Doctor . She arrives at the Pavilion in the aftermath of Grendel ' s attack , which has left Lamia dead , and helps the Doctor flee ; but the situation is soon reversed as Grendel succeeds in destroying the Reynart android and then recapturing the errant Romana . Part 4 . The evil Count now wishes Romana ( as Strella ) to marry the real King , who will then be killed , leaving Grendel free to take her hand himself and be declared the legitimate King of Tara . Worried by the length of time a siege would take , the Doctor resorts to other means to get his friends back from Castle Gracht . K9 is used to help them gain access to the castle by means of the moat and underground tunnels . The Doctor reaches the throne room just in time to stop the sham Reynart marriage to Romana . He then engages the Count in a deadly duel with electro - swords , defeating him and forcing the villain to jump into his own castle moat and swim for his survival . Romana has meanwhile freed Strella and the royal party is united , with Grendel disgraced and presumably on his way to exile . It is a time of reunions : Reynart with his love Strella ; and the Doctor and Romana with the fourth segment of the Key and the TARDIS — once K9 has been retrieved from a rowing boat in the middle of the moat . Home video and audio releases . DVD releases . Contents ( 2007 / 2009 version ) : Notes :