Part of that timeslot was originally meant to be Bakeoff, of all things! Maybe the fact it's first showing did OK against Corrie Live means that they decided the repeat wasn't needed, so they gave the slot to the Doctor instead?
Any reason for the usurping of the afternoon schedule on BBC ONE with a repeat showing of both EPs 1 and 2 of this new series tomorrow afternoon?
I imagine in part because the overnight ratings were only 3.8m due to England v Wales rugby match. I think episode 1 ratings were also down slightly, possibly due to the rugby. Not sure how many people will watch though due to it being a late schedule change.