Actress Keeley Hawes has been announced to play a new villain in Series 8 called 'Ms Delphox'.
http://www.doctorwhotv.co.uk/series-8-keeley-hawes-cast-as-ms-delphox-61735.htm
"Keeley Hawes is having one heck of year. And now it’s about to get even better as she achieves the greatest villainy yet attempted on Doctor Who: she plays a banker." ~ Steven Moffat.
Sounds interesting.