Jon Pertwee played the Doctor
for just over 4 years, from January 1970 to June 1974. This era was the
first to be made in colour and saw the Doctor teaming up with the United
Nations Intelligence Taskforce (UNIT) under the command of Brigadier Lethbridge-Stewart
(Nicholas Courtney) . It also saw the introduction of the Doctors' 'arch-nemesis',
the Master, played by Roger Delgado. Pertwee relinquished the role to
Tom Baker in 1974.