The early 1970s, arguably, was when Doctor Who started to come of age, and a lot of the credit belongs to the late, great producer Barry Letts.
The Beginning and the End of Doctor Who's "UNIT Family" Era
R.I.P. Barry Letts, The Man Who Made Doctor Who Transcendental
Barry Letts, the producer of Doctor Who from 1970 to 1974, died at the age of 84. He was responsible for introducing Buddhist themes and ideas to the series during the Jon Pertwee era, and also cast Tom Baker as the fourth Doctor. I will always think of his strange, wonderful moment in the Doctor Who And The Daemons…
