The casting of the role of The Doctor is, inarguably, the
most important decision undertaken by anyone involved in 'Doctor Who', on any
level. Stories were commissioned and placed in an early phase of
pre-production, first by the show's story editors, and then later, by script
editors, the job title being altered to more accurately reflect the
individual's duties. But these scripts always featured a vague, undefined
'Doctor' absent the mannerisms, personality traits, even physical descriptions
that can only come with an actor cast in the role. Terrance Dicks, former
script editor of the show during the early to mid 1970's, reflected that it was
only after meeting and speaking with Tom Baker upon his official acceptance of
the role did he begin to explore the character possibilities of the Fourth
Doctor; prior to that, the stories did not jump off the page.