In the next few episodes, she plays Joan Redfern, matron at a boys' boarding school in 1913. For reasons too complicated to explain here, the Doctor is living under the name John Smith, unaware that he is the Doctor.
It was 'next few episodes' bit that surprised me. Possibly the reporter misunderstood what she said, but it's unusual to for the new Who to stay in one place for so long.
Also I don't usually read spoilers, so this might be well known already.
ETA - Yipes, just remembered it's H's dad's 75th Birthday tomorrow, so I won't get to see it anyway.