Filming for Doctor Who 7×04 is currently taking place in Cardiff Bay, Wales. Freshly leaked pictures give us a look at a returning guest star, some explanation as to the episode’s title, and The Doctor on a slide! This post contains spoilers.

The production team returned to the house that masquerades as Amy and Rory’s home, with Mark Williams joining them! We already knew that the Harry Potter actor would be appearing as Brian Williams, Rory’s father, but this now seems to confirm that the role will be recurring. We also got a second glimpse at the UNIT soldiers, after it was revealed earlier on in the week that they would be returning to the show.

This week also saw the episode title revealed as “Cubed,” and rather unsurprisingly, there seems to be an abundance of black cubes littered around the Ponds’ street. In one picture, Brian Williams can be seen clutching one of the aforementioned objects. Another shows The Doctor examining one with a magnifying glass while perched in a tree.

The episode may be the last that Karen and Arthur will film for Who, but there was still plenty of joking around going on between the cast members. Twitter user Mugnim0e (who has been taking a LOT of pictures throughout the whole filming process of the seventh series) shared the shots as well as a video, and told fans that Karen and Arthur had been singing while leaning out of a window. Matt Smith was also seen playing around on a slide in a children’s park.

Take a look at the images and video below!

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Are you glad to see that Mark Williams will feature in more than one episode? What do you think the cubes mean?