Rachel Jensen (Pamela Salem), Allison Williams (Karen Gledhill), Sir Toby Kinsella (Hugh Ross) and Group Captain Gilmore (Simon Williams) in the cover illustration for the Counter-Measures box set released in July 2016.
It’s 1963, and opposing factions of Daleks are battling it out on the streets of east London. Caught in the middle of this conflict, the Seventh Doctor (Sylvester McCoy) and Ace (Sophie Aldred) team up with two scientists – Professor Rachel Jensen (Pamela Salem) and her assistant Allison (Karen Gledhill). Meanwhile, Group Captain Gilmore (Simon Williams) of the British Army evacuates the area, and to avoid mass panic he keeps it low key. He doesn’t tell the people of Shoreditch there’s an alien invasion, instead making use of the peace-time nuclear accident provisions under the aegis of the Counter-Intrusion Measures, United Kingdom. The Daleks are defeated, and the Doctor and Ace discreetly disappear. Gilmore, Jensen and Allison form a specialist Counter-Measures group to investigate strange phenomena and prevent further invasions...
That last bit, by the way, happens off screen, in a series of audio adventures.