ties or cravats. Beginning in the 1971 season, when the look was refashioned by Ken Trew, Pertwee wore a red jacket and a cloak with purple lining. In the final two seasons, the colour scheme changed from story to story, though the basic look was maintained. In his first episode, when the Doctor evades capture by taking a shower, a tattoo of a serpent can be seen on his arm. Whereas Pertwee obtained it during his service in the Royal Navy, an in-universe reason for it was eventually provided in the New Adventures novel Christmas on a Rational Planet as being a Time Lord symbol signifying exile, removed once the Doctor's exile was formally ended following the events of The Three Doctors. Story style The Third Doctor stories were the first to be broadcast in colour. The early ones were set on Earth because he had been exiled there when the Second Doctor was banished to Earth by his people, the Time Lords, and forced to regenerate. On Earth, he worked with the Brigadier and the rest of the UNIT team. However, as his tenure progressed he had reasons to leave Earth, on occasion being sent on missions by the Time Lords. Eventually, after his defeat of the renegade Omega in The Three Doctors, he was granted complete freedom by the Time Lords in gratitude for saving Gallifrey. The Third Doctor's era introduced adversaries including the Autons, the Master, Omega, the Sontarans, the Silurians and the Sea Devils. The Daleks returned after a five-year absence about halfway through Pertwee's run. The Third Doctor was the only one from the classic series not to have a story featuring the Cybermen (although they were seen briefly in The Mind of Evil and Carnival of Monsters), but he did eventually encounter them during The Five Doctors. "Reverse the polarity of the neutron flow" A catchphrase used during the Third Doctor's era was "reverse the polarity of the neutron flow". The phrase was Pertwee's way of dealing with the technobabble that he was required to speak as the Doctor. Terrance Dicks recalls that he had used the line in a script, and Pertwee approached him about the line. Dicks had feared that he would have to remove it, but Pertwee stated that he liked it, and wanted to see it more often. Dicks obliged. The Third Doctor only said the full phrase "reverse the