Apollo 13 launched on April 11, 1970. Two
   days after the launch, the spacecraft was
   crippled by an explosion, The crew used the
   Lunar Module as a “lifeboat” and successfully
    returned to Earth on April 17.

This was the John Pertwee and Tom Baker era; it marked the beginning of coloured
television, and for many people, what we saw during this time has never been surpassed. 

Important changes now took place. The seventh season, the first
to feature John Pertwee, was cut to a run of twenty-five episodes;
each season would now be between 20 and 28 episodes, a pattern
which would  last  until  the  middle of the 1980s.  Another new
feature was the introduction from the eighth season onwards of
the  renegade  Time Lord  known as the Master,  played by the
superb  Roger  Delgado.  His  role  was that of the  criminal
mastermind,  a ‘Professor  Moriarty’  to the  Doctor’s  Sherlock
Holmes. The scenes  between  these  two  great characters are 
legendary. The  Master was pure evil. However, the Doctor would
always thwart his  diabolical  schemes, but of course the Master
would escape to fight another day. 

A new era also meant a new format. The Doctor was now banished
to earth by his own people the Time Lords; this meant the Doctor
could  no-longer  freely  move  around  in time  and space.
His adventures  would now be  earthbound. This allowed for the
incorporation  of  UNIT  (United Nations Intelligence Taskforce)
into the plotlines. The likes of the Brigadier and Sergeant Benton
now became  regulars and the Doctor signed on as their scientific advisor.  It worked  brilliantly. However,
after two fantastic seasons programme makers soon tired of the  format, and sought reasons  for the 
Doctor to continue  travelling  in  time and space, eventually having the Time Lords grant him full freedom
at the conclusion of the 1973 story, the Three Doctors. 

John Pertwee was replaced by Tom Baker in 1974.  Tom stayed for seven glorious years, a time-span longer 
than any of his predecessors, but still not long enough. During this time viewing figures were consistently
high and the show reached new heights of popularity. Tom Baker is without doubt the most popular and 
best-remembered of all the Doctor’s. This man simply had it all; the booming theatrical voice, an infectious
smile, a twenty-foot scarf and that big bag of jelly babies. It was a winning formula. The finest stories 
originate from this era: Robot, Sontaran Experiment, Pyramids of Mars, Horror of Fang Rock, State of Decay,
Genesis, Talons, Destiny… You all know what I mean. They are all-time classics!