Doctor Who: The Vanquishers (Flux 6)

And as I understand it, with this finale, Chris Chibnall bows out, since the New Year's Special will be written by our once and future Welsh Overlord.

ETA: Turns out I was misinformed: three more Chibnall-written specials, then the RTD takeover.

( Spoilers suddenly realise no one in six episodes has brought up the Flux Compensator! )