Doctor Who is introducing the Doctor's replacement as UNIT's Scientific Adviser. Regeneration has always afforded Doctor Who the opportunity to reinvent itself. The ultimate illustration was in 1969, when Patrick Troughton's Second Doctor summoned the Time Lords to help him with a crisis — and, in addition to experiencing a forced regeneration, the Doctor was exiled to Earth. Unlike previous incarnations, Jon Pertwee's Third Doctor was stranded on a single planet, and he soon wound up working with an organization called UNIT.
UNIT, the United Nations Intelligence Taskforce — or, sometimes, the UNified Intelligence Taskforce — had previously been introduced in 1968's "The Invasion." Run by Brigadier Lethbridge-Stewart, UNIT's job was to deal with the strange and unexplained; that naturally meant the Doctor was an almost-perfect fit, and he swiftly became their Scientific Adviser. The Doctor remained allied with UNIT even after he regained the ability to travel in time, with most Doctors teaming up with UNIT or Lethbridge-Stewart. Although he never technically resigned, 1989's "Battlefield" nonetheless revealed the Doctor had been struck off, probably because he was simply too unreliable.
But it seems UNIT still needed a Scientific Adviser. Big Finish has released details of an upcoming audiobook, UNIT: Brave New World — Seabird One. Set before the events of "Battlefield," it stars Angela Bruce as Lethbridge-Stewart's replacement Brigadier Winifred Bambera, reprising her role from the TV series. In the aftermath of the Cold War, Bambera is offered a job as the new head of UNIT. She winds up working alongside experienced UNIT Sergeant Jean-Paul Savarin and "UNIT’s rebellious new scientific adviser," Dr. Louise Rix. The stories sound to be centered on the rocky relationship between Bambera and Rix, particularly when there are claims the ghost of one of Rix's old colleagues is haunting the launch of a new British space station.
It's easy to forget that Doctor Who's Earth isn't quite the same as our own. The original Pertwee-era UNIT stories featured several stories in which humanity possessed advanced technology — and included a manned British mission to Mars (which, of course, turned into a first contact situation). Big Finish's UNIT: Brave New World — Seabird One clearly takes advantage of this idea, incorporating real-world events like the collapse of the Soviet Union and the fictional launch of a British space station in the early '90s.
It will certainly be interesting to meet Dr. Louise Rix. She's an original character never seen in Doctor Who lore before, and it's entirely possible her time with UNIT will be brief, explaining why she wasn't on hand in "Battlefield." Whatever the case, though, the Doctor established the idea of UNIT's Scientific Adviser as essentially a rival power to the Brigadier running UNIT at any given time, so Bambera is sure to clash with Rix in this exciting Doctor Who tie-in.
Source: Big Finish