Invasion of the Dinosaurs ( TV story ) Invasion of the Dinosaurs was the second story in season 11 of " Doctor Who " . This story marked a significant plot twist : Captain Mike Yates betrayed UNIT as a result of his traumatic experience in " The Green Death " . As punishment , he was dismissed from UNIT , but Brigadier Lethbridge - Stewart was sympathetic and arranged for the lessening of his punishment . Yates was made to go on an extended sick leave and given the opportunity to make a quiet resignation , granting him the mercy of a graceful departure in exchange for his past service as a loyal officer . Following this event , it was Richard Franklin ' s last regular appearance before returning to do a sendoff performance for his character in " Planet of the Spiders " , the Third Doctor ' s regeneration story . It also saw the debut of the Third Doctor ' s second and noticeably more advanced car , the Whomobile . The commissioning of this car was the result of Jon Pertwee ' s love for gadgetry and the spy culture in general . However , it was used only once more during his tenure , with Bessie remaining the Doctor ' s chief road vehicle of choice . Synopsis . The Third Doctor and Sarah arrive in 1970s London to find it has been evacuated because dinosaur s have appeared mysteriously . It turns out the dinosaurs are being brought to London via a time machine to further a plan to revert London to a pre - technological level . Plot . " Invasion " part one . The Doctor and Sarah Jane Smith arrive in a deserted London plagued by looters and lawlessness . UNIT is helping maintain martial law . The regular army , headed by General Finch , has evacuated the city and issued orders to shoot looters on sight . the Brigadier disagrees , since it meant shooting civilians . The Doctor and Sarah encounter several looters and , surprisingly , a pterodactyl . The two are then arrested on suspicion of being looters . The Doctor is designated as Prisoner 177781 and Sarah Jane Smith is designated as Prisoner 177782 . Outside , a tyrannosaurus rex destroys a building and traps some soldiers . They manage to drive it off . At the school serving as UNIT HQ , the Brigadier and Benton discuss the interference problems with their communications and look at the latest pictures of looters , which include the Doctor and Sarah . The Doctor and Sarah escape but are caught by soldiers . They are loaded into the back of a Land Rover to be taken to the detention centre . The Land Rover encounters a tyrannosaurus rex . Part two . While the soldiers fight the tyrannosaurus , the Doctor and Sarah escape and hide in a garage . They find a medieval peasant from the days of King John already there who , believing the Doctor to be a wizard who has put a spell on him , attacks the Time Lord with a knife before disappearing in a time eddy . Soldiers search the area , the Brigadier enters the garage . Back at UNIT HQ , the Brigadier explains the situation to the Doctor . Dinosaurs appear and disappear , the city has been evacuated , and looters run rampant . The Doctor is introduced to Finch , who is in charge of the operation . Finch doesn ' t think the Doctor will be much help , but rather finds his ideas unrealistic . Sarah talks with Mike Yates , who needed some time off after the experience with the giant maggots . A stegosaurus has been trapped , and the Doctor wants it taken alive . However , it disappears in a time eddy that makes time run backwards . The people affected would not remember it happening . The Doctor suspects someone is deliberately bringing the dinosaurs to London — and in a hidden laboratory a pair of scientists , Butler and Professor Whitaker , are operating the time technology causing the situation . They are aided by Mike Yates , who feels the Doctor could help them achieve Operation Golden Age , but Whitaker is unconvinced . He tells Mike to sabotage the stun gun the Doctor is building to use on the dinosaurs . The Doctor believes the dinosaurs are a distraction by someone who needs London evacuated . When a brontosaurus appears , he heads out to capture it . Mike sabotages his stun gun , and it doesn ' t work on the brontosaurus . The time eddy takes away the brontosaurus , and a tyrannosaurus appears behind the Doctor . Part three . The Doctor falls , dropping the gun , which Yates picks up . He undoes his sabotage and fires at the tyrannosaurus . The creature is captured and brought back to a hangar . Yates is angry at Butler and Whitaker for trying to kill the Doctor but agrees to performs further acts of sabotage — specifically against the machinery being used to record from where the dinosaur appearances are controlled . Sarah has been doing some research into time travel and mentions Whitaker . The Brigadier remembers the name , and the Doctor wants to check up on him . The tyrannosaurus is freed by Finch , who breaks its chains . Sarah is attempting to take pictures of it when it awakes and moves to attack her . She find the door has been locked from the outside . Before the dinosaur can get to Sarah , the Doctor finds and rescues her . She then sets off to gather her own evidence . Sarah meets with Sir Charles Grover , an ecologist MP who is acting Minister with Special Responsibilities in London . He drugs her . When she wakes up , she is astounded to find herself on a vast spaceship . Part four . The crew of the ship includes Mark , Adam and Ruth , minor British celebrities who have adopted new aliases and lives . They tell her they are en route to a New Earth where mankind can begin again , closer to nature . They left Earth three months earlier ; the ship is one of a fleet carrying over two hundred people to a new life . Sarah is committed to the re - education programme to enable her to think like them . The Doctor searches London in his new vehicle , the Whomobile . Under Moorgate Station , he finds the base used by Whitaker and Butler but is scared away when they use a pterodactyl to defend it . He returns with the Brigadier , but all signs of occupation have been removed . Operation Golden Age is revealed to be a broad conspiracy including Whitaker , Butler , Yates , Grover and Finch as its core coordinators . They have emptied London to let it to revert to a more natural state , after which the people on the spaceships — in reality in vast bunkers — will be allowed out to repopulate a clean and free planet . Whitaker also works out how to reverse time , so soon humanity , apart from their own chosen specimens , will never have existed . Finch tries to frame the Doctor , who he knows will not support their plans . He brings the Brigadier to the Doctor , catching him in the act as a new time eddy starts up . Part five . The Doctor soon twigs that an over - zealous Yates is the UNIT mole . Sergeant Benton lets the Doctor escape , for which Finch threatens a court martial . The Doctor uses his freedom to track down more monsters , but when he is recaptured , the Brigadier asserts his authority and takes the Doctor into UNIT custody rather than the regular army ' s . Meanwhile , Sarah has escaped from the fake spaceship . She has learnt its true nature . She is caught by Finch , who returns her to Whitaker ' s custody . While she is away , Mark works out that the ship is a fake and tells the other passengers , but he is not believed . When Sarah is returned to the ship , Mark and she use the fake airlock to convince Ruth and the others of the deception . The Doctor encounters another time eddy and is faced by more dinosaurs . Part six . The dinosaurs start fighting each other . Finch arrives and tries to take the Doctor , but Benton and the Brigadier arrive as well and take the Doctor away . Shortly afterward , Yates arrives and holds the Doctor , Benton and the Brigadier at gunpoint . He reveals the nature of their plans . Yates is distracted when Private Bryson enters with a tea tray and offers the Captain a cup , giving Benton the opportunity to disarm Yates . Sarah is able to convince the occupants of the fake spaceship that they have been duped by opening the airlock . They confront Whitaker and Grover and demand an explanation . Grover attempts to placate them , but the Doctor and Brigadier arrive . Whitaker breaks free of his captor and pulls the lever , activating the reversal process . A Time Lord immunity allows the Doctor to undo this . He then reverses the polarity , but Grover does not recognise this and pulls the switch himself . Whitaker tries to stop him , and both are transported back in time to their " Golden Age " . Back at UNIT HQ , the Brigadier confirms that the crisis is over , but there are still human casualties to deal with . Finch will be court - martialed . Yates is offered the chance to resign and given extended sick leave . The Doctor reflects that people like Grover may have had good motivations in wanting to fight pollution and environmental degradation , but they took their schemes too far and endangered all mankind and its civilisation . He decides it is time for a holiday and offers to take Sarah Jane to the beautiful planet of Florana . Home video and audio releases . Digital releases . This story is available :