It had originally been intended that Peter Bryant, after recovering from a period of ill health, would return to Doctor Who to produce the whole of the seventh season. In the event, however, he, Derrick Sherwin and Trevor Ray were all assigned around the beginning of October 1969 to revamp the problematic Paul Temple series.
Bryant was consequently involved with the production of only the first two stories of the season, eventually transmitted under the titles Spearhead from Space and Doctor Who and the Silurians, and received a credit on neither: the producer's credit on the former went to Sherwin, and that on the latter to Bryant's eventual successor - Barry Letts, whose only previous work on the series had been directing The Enemy of the World for the fifth season. Letts had been invited to take on the job, after a number of others (including Douglas Camfield) had turned it down, and agreed on condition that he would also be allowed to direct at least one story per season.
Terrance Dicks remained as the series' script editor and quickly struck up an excellent working relationship with Letts. Trevor Ray meanwhile was briefly replaced by Robin Squire - a young former pop singer who had written a novel about the music business and gained an attachment to the production team - until he too moved on and the assistant script editor post was dropped.
Although Bryant and Sherwin formally oversaw only the first part of the season (which, consisting of only twenty-five episodes, was by far the shortest to date), their influence was strongly felt throughout. For one thing, it was Bryant who had cast Jon Pertwee and set the parameters for his characterisation of the Doctor (although in the event the actor gave a far less whimsical performance than Bryant had envisaged). For another, it was Bryant and Sherwin who had chosen to overhaul the series' format by having the Doctor exiled to Earth and allied with UNIT in a succession of relatively adult-orientated adventures. It was they, too, who had decided to introduce a sophisticated Cambridge University scientist as the Doctor's new assistant rather than another of the naive youngsters who had tended to be his companions in the recent past.
The following production block would see Letts bringing much more of his own influence to bear on the series, leaving season seven as a tantalising glimpse of how Doctor Who might have continued had Bryant and Sherwin remained in charge.
It seemed at one point that Doctor Who's seventh season might be its last. Barry Letts was informed during the course of its production that his BBC superiors were seriously considering cancelling the series and wanted him to come up with a suggestion for a possible replacement. He devised an idea entitled Snowy Black concerning the exploits of an innocent Australian cowboy trying to come to terms with city life in London - a forerunner of sorts to the Crocodile Dundee films of the mid to late eighties - and even got to the point of lining up an actor, Mark Edwards, to take the title role. Before the first scripts were commissioned, however, Doctor Who was finally confirmed for a further season and Snowy Black was no longer needed.
Although pleased that the style of Doctor Who had shifted away from science-fantasy toward science-fiction, Letts disliked the idea of the series' stories being set almost exclusively on near-contemporary Earth and determined to have the Doctor journeying once more into space and time. Terrance Dicks strongly supported this move, finding himself much more in tune with Letts's ideas than he had been with Peter Bryant's and Derrick Sherwin's.
Another element of the seventh season with which both Letts and Dicks had been dissatisfied was Liz Shaw. This was on the basis that the independent, self-confident scientist had little need to rely on the Doctor for explanations and so, in their eyes, failed to fulfil the basic dramatic functions of aiding plot exposition and acting as a point of audience identification. Letts therefore decided against renewing actress Caroline John's contract for a further season and the two men set about devising a new companion for the Doctor. Other changes also lay in store as the series underwent what was, in effect, a further revision of its format for the eighth season.