We still don't know what Peter Capaldi will be wearing for his regular Twelfth Doctor duds, but in this video from the set, he's been spotted wearing white pajamas while on horseback.

Doctor Who TV has a couple of photographs from the set where you can actually see Capaldi in his costume, but they also report that he's the one riding the horse through the Victorian era streets. Below is a video of his stunt double on horseback:

And Doctor Who TV reports that Strax was also spotted on horseback, although lord knows what he thinks he's riding.

Series 8 Filming: Capaldi in Action! [Doctor Who TV via Blastr]