The Third Doctor is an incarnation of the Doctor, the protagonist of the BBC science fiction television series Doctor Who. He was portrayed by actor Jon Pertwee. Within the series' narrative, the Doctor is a centuries-old alien Time Lord from the planet Gallifrey who travels in time and space in the TARDIS, frequently with companions. At the end of life, the Doctor regenerates. Consequently, both the physical appearance and personality of the Doctor changes. Pertwee portrays the Third Doctor as a dapper man of action in stark contrast to his wily but less action-orientated predecessors. While previous Doctors' stories had all involved time and space travel, for production reasons Pertwee's stories initially depicted the Doctor stranded on Earth in exile, where he worked as a scientific advisor to the international military group UNIT. Within the story, the Third Doctor came into existence as part of a punishment from his own race, the Time Lords, who forced him to regenerate and also disabled his TARDIS. Eventually, this restriction is lifted and the Third Doctor embarks on more traditional time travel and space exploration stories. His initial companion is UNIT scientist Liz Shaw (Caroline John), who unceremoniously leaves the Doctor's company between episodes to be replaced by the more wide-eyed Jo Grant (Katy Manning), who then continues to accompany the Doctor after he regains use of his TARDIS. His final companion is intrepid journalist Sarah Jane Smith (Elisabeth Sladen). Personality The Third Doctor was a suave, dapper, technologically orientated and authoritative man of action who practised Venusian Aikido. A keen scientist, he maintained a laboratory at UNIT where he enjoyed working on gadgets in his TARDIS. In his spare time, he was fond of motoring, handling all manner of vehicles. His favourite car was a canary-yellow vintage roadster that he nicknamed "Bessie", a machine which featured such modifications as a remote control, dramatically increased speed capabilities and inertial dampers. He also maintained a hovercraft-like vessel that fans nicknamed the Whomobile. The First Doctor, upon meeting the Third, described him indignantly as a "dandy", while the Second Doctor, with whom the Third had something of an antagonistic relationship on the occasions they encountered each other, referred to him as "Fancy Pants". While this incarnation spent most of his time exiled on Earth—grudgingly working as UNIT's scientific advisor—he was occasionally sent on covert missions by the Time Lords, where he would often act as