It looks like Russell T. Davies, showrunner for Doctor Who, has plans to expand on the franchise’s universe along with BBC and Disney+, with new details on a Kate Stewart-focused spin-off emerging online. Kate Stewart, who is played by Jemma Redgrave, is the daughter of Brigadier Lethbridge-Stewart, who has appeared in 10 episodes so far.
Kate’s father, the Brigadier, is known across the Whovian community for playing a loyal character to The Doctor, starring in over 20 episodes from 1968, with various references and throwbacks to his character being featured in the show since his departure.
New spin-off details come from The Daily Mirror via BBC, with information about a Kate Stewart-focused spin-off series that will be centred around the U.N.I.T. military organisation, which makes sense as Kate Stewart is the leader of the U.N.I.T. division, short for Unified Intelligence Taskforce – more details below.
It has also been speculated that Redgrave’s Kate Bishop will also be appearing in this year’s Doctor Who Christmas special, starring the new Doctor played by Ncuti Gatwa (Sex Education, Barbie). David Tennant and Catherine Tate will also be starring in three already-announced Doctor Who 60th-anniversary episodes.
Additional ‘Doctor Who’ Kate Stewart Spin-Off Details

Jemma Redgrave’s Kate Stewart has been detailed in these new details as being the head of scientific research at U.N.I.T., the role that Doctor Who fans best know her for since she joined the franchise in 2012.
Russell T. Davies will be at the helm as showrunner, not only for the main Doctor Who series but also for any spin-off projects that are currently being planned to expand on the “Whoniverse” with BBC and Disney Plus.
Although Stewart is the main focus of the spin-off, it is possible that the show may dive back into the roots of U.N.I.T., as the fictional military organisation has been in Doctor Who since the late 1960s, both canonically and literally.
A release date for the newly revealed spin-off series has yet to be announced, however, it has been stated that it won’t be launched before Ncuti Gatwa’s introduction as The Doctor during the 2023 Doctor Who specials. The Daily Mirror also noted that talks on a spin-off series based on U.N.I.T. in the 1970s have also been reported in the past, however, it seems that the studios are taking the original idea to a slightly different place in the Doctor Who timeline.
The three Doctor Who 60th-Anniversary special episodes are set to air in November of 2023.
Source: The Daily Mirror