During his interview with Empire Magazine Steven Moffat commented on why Series 8 needed a bit of a shake up:
It was time to change. Certain things we were doing a little reflexively. Some of the humour was getting a bit glib. One of the hardest things to notice is when your new idea has become your old idea and it’s time to get rid of it.
Jenna Coleman, who plays Clara, added:
It’s amazing how different it feels. It’s darker. The limits feel like they’re being pushed more in terms of the danger and the dread. It’s scarier, that’s for sure.
Coleman then went on to say that the pace of the stories has changed. Explaining that we can expect much longer scenes in this new format for the show.
Moffat agrees saying that the opening episode has a scene in it, which happens to be his favourite, which is set around a five minute argument with the Doctor and Clara over a restaurant table.
Director of the first two episodes, Ben Wheatley, concluded by saying:
For me, they’re back to Classic Who, or the mid-Tennant adventures, where you’d tell a story and move on to the next one, less tied up in the final machinations of long plot arcs.
Capaldi’s his own man but there are elements of Baker and Troughton and Pertwee. He’s inherently funny but inherently brooding and complicated, as a performer and a man.
[Source: Doctor Who TV]