Russell T Davies has shared an update on the upcoming Doctor Who spin-off, The War Between the Land and the Sea. It is understood the series, featuring the return of UNIT and the Sea Devils, has entered the third week of filming, which is expected to last until December.
Writing for Doctor Who Magazine (per ScreenRant), Davies had this to say:
“In the office, this show is generally shortened to TWB, which makes me think it stands for Torchwood: Birmingham. We’re in the third week of filming. Very exciting!”
“The shoot will go on until just before Christmas, and it’s a mammoth task, all wrangled by one director, Dylan Holmes Williams. I wrote eps 1 and 5, Pete McTighe wrote eps 2 and 3, and ep 4 is by both of us. Shooting a miniseries as one block brings its own challenges.”

Later, Davies discussed the schedule to produce the spin-off. The showrunner teasingly highlighted that “an actor” would appear in the fifth and final episode of the series (without name-dropping them), subsequently adding to the logistical nightmare of shooting the series.
“Normally, five episodes would be broken down into two or three blocks, filmed roughly in order. But this is all one big block, so an actor could appear for the first time in the very last scene of the very last episode (and indeed, someone does), but we could need them to shoot tomorrow,” Davies wrote.
“Equally, someone could be needed in ep 1 sc 1, but maybe we won’t shoot that until December. Logistics galore. When you see all those names listed in the credits, that’s people hammering this into shape, with smoke and steam hissing from the joints as they batter the schedule with big hammers! Production! It’s brutal!”