While Jenna Coleman, who plays the Doctor’s assistant, Clara, was not glimpsed on the set, Capaldi was joined by guest star Michelle Gomez, who was portraying “the Gatekeeper of the Nethersphere.”
Wales Online captured a large number of photos of the location filming at The Friary in the middle of Cardiff, but I put the gallery after the cut because the images are very spoilery.
Yes, these photos show not only the Cybermen and U.N.I.T. but Kate Lethbridge-Stewart (Jemma Redgrave), last seen in the 50th anniversary story, “The Day of the Doctor.” Also, just behind Kate, I believe I spy DotD’s Osgood, the UNIT scientist played by Ingrid Oliver, this time sporting an 11th Doctor-inspired bow tie instead of a Fourth Doctor scarf!
You may also notice that the decapitated Cyberman head on the ground between Kate and the silver giants is clearly an older version (perhaps from the Black Archive?) while the invading army is the updated post-“Nightmare in Silver” version.
As for the presumed-villainess with the Doctor, Executive Producer Steven Moffat said of Gomez:
I’ve known Michelle for years, and I’m thrilled to welcome her to Doctor Who. She’s everything we need – brilliant, Scottish, and a tiny bit satanic.
In between shooting, Capaldi and the Cybermen actors posed for photos with the huge number of fans who lined the perimeter of the set.