Following the announcement earlier in the day of the casting of Michelle Gomez as the Gatekeeper of the Nethersphere, the show's official Twitter account subsequently tweeted a behind-the-scenes picture showing Gomez with Peter Capaldi in Cardiff and Cybermen behind them.
It is believed they were shooting scenes for the Series 8 finale.
Doctor Who returns on Saturday 23rd August.
Doctor Who Official : Look who's back . . .
The picture was tweeted again a few hours later with the words: "In case you missed it … Peter Capaldi, Michelle Gomez and some familiar faces, earlier today!"