Letts' first involvement with
Doctor Who was in 1967 when he directed the
Patrick Troughton serial
The Enemy of the World. This was a complex serial to direct as Troughton played both
the Doctor and the dictator "Salamander" in the same story and sometimes in the same scenes – a rare and demanding directorial requirement for the 1960s. However, in his memoir
Who and Me, Letts related how he naively used
matte boxes to allow Troughton to act face to face with himself, when in fact
optical printing was already available and the same could have been accomplished in post-production. He became the series' producer in October 1969, replacing
Derrick Sherwin, with
Jon Pertwee recently cast as the Doctor. Letts' first story as producer was Pertwee's second,
Doctor Who and the Silurians, and he remained the producer for the rest of the Pertwee serials, becoming the father figure in the 'family' atmosphere that had developed on the show at that time. It was an era of substantial change for
Doctor Who, with episodes broadcast in colour for the first time and an improved budget which enabled more location filming and action sequences than had previously been possible. Letts also embraced the technological innovations which came with moving the series into colour, most notably his enthusiasm for
Colour Separation Overlay. He also oversaw the celebration of the programme's tenth anniversary in 1973, uniting the first three Doctors in the first multiple Doctor story,
The Three Doctors. When he took over, a recent BBC decision had cut the season length from over 40 episodes a year to 26. Notable changes Letts made, as related in his autobiography
Who and Me, included producing the show in two-episode blocks, rather than as separate episodes: rehearsing two episodes for a fortnight, and then recording those two episodes back-to-back, thereby reducing the demands on the studio scenic crews, who only had to erect and strike the sets once a fortnight instead of once a week. This was a profoundly significant change: it allowed much more rehearsal time, in a much less frantic atmosphere; it ended a long running dispute with the unions representing the technical crews; it reduced wear-and-tear on the sets (and the budget allocations for repairing the damage); and it meant that, forever after, serials could only be made in multiples of 2 episodes—a primary reason for the 4-episode and 6-episode format dominating the schedules for the following fifteen years. He also retired the original
howl-around title sequence used, with variations, from 1963 until 1973, introducing as its replacement the classic
time tunnel special effects sequence which would run, until 1980, behind the opening and closing credits for every episode produced in seasons 11 to 17. When he was offered the chance to become producer on the series, Letts made it a condition that he be allowed to also continue to direct. The Head of Serials agreed to this, and Letts directed three
Doctor Who serials during his time as producer:
Terror of the Autons,
Carnival of Monsters and
Planet of the Spiders. Letts also directed most of the studio scenes for
Inferno after
Douglas Camfield was taken ill during the production. Letts's final work as a director on the series was when he returned in 1975 to direct
The Android Invasion during the era of
Philip Hinchcliffe as producer. Letts formed a particularly close partnership with two other contributors to the programme:
Terrance Dicks, who was the script editor on the programme between 1968 and 1974; and playwright
Robert Sloman, with whom Letts co-wrote four serials in the Pertwee era:
The Dæmons (credited under the pen-name Guy Leopold);
The Time Monster;
The Green Death; and
Planet of the Spiders, which was Pertwee's swansong. Letts later provided an official obituary for Sloman in December 2005, published in
The Guardian. Letts was a
Buddhist and also held
liberal political views. According to
Toby Hadoke, who contributed to his
Guardian obituary, "Letts's liberal worldview led him to commission stories with contemporary resonance – eco-parables, critiques on
colonialism and
apartheid, even entry into the
Common Market (the Galactic Federation in
Doctor Who parlance) were all presented within a format of child-friendly derring-do." and
Island of Death (2005). He, like Terrance Dicks, also wrote radio dramas for the
Big Finish company's series of productions starring Elisabeth Sladen as Sarah Jane Smith, released on CD. In 2008, he performed an unabridged audiobook reading of his novelisation of
The Dæmons. In June 2008 he recorded a long in-vision interview covering his entire career, and his
Doctor Who years in particular, excerpts of which continued to be widely used on future DVD releases, most notably on an obituary documentary "Remembering Barry Letts" which was included on the BBC DVD release of
The Dæmons. He continued to record commentaries and interviews for DVD releases of his
Doctor Who episodes until shortly before his death in 2009. His involvement with
Doctor Who was far wider than simply his professional work of writing, directing and producing the show. He frequently gave interviews, attended conventions, and made personal appearances in connection with the show and his work on it and indeed other aspects of his career. He enjoyed a lifelong friendship with Terrance Dicks, established in 1969, and they frequently attended events as a team. Letts' work on the show is inextricably linked with the character of the
Third Doctor, as played by
Jon Pertwee. With the exceptions of
The Enemy of the World,
Robot,
The Android Invasion and his one season as executive producer in 1980–81, every
Doctor Who story regardless of media in which Letts has been involved – whether as producer, director or writer – involved this version of the character. ==Later work==