I'm seeing something between Servalan and Harriet Walter (as Harriet Vane). This, as any fule should kno, is a compliment.
My immediate thought was Dannii Minogue.
It has been observed that the difference between the Minogue sisters is thus:
Kylie looks as if she might.
Dannii looks as if she already has.
To be fair, this was in Dannii's regrettable lads-mag phase and she is actually quite classy now.