Steven Moffat has spoken a little about the story arc this year stating that it will only take up a small chunk of each episode in the lead up to the finale. Think Series Five, rather than Six.

Responding in EW, Moffat said: “Yes [there are over-arching plotlines], but at the same time 90 percent of every episode is a stand-alone adventure.”

On the overall setting of each episode: “We’ve got quite a lot of Earth stuff this time. But it’s proper variety, and I think i’ll not tell you what’s going to be on the roller coaster in advance.”

Teasing the big two-part finale he says: “It’s not just about the Cybermen. It’s a good, action-packed, mad one.”