Stephanie Hyam played Heather, and the sentient oil taking Heather's form, in the Doctor Who television stories The Pilot and The Doctor Falls.
Outside of Doctor Who, Hyam played Charlotte Murray in Peaky Blinders and Lily Clarke/Carew in Jekyll and Hyde.
Additionally, in Steven Moffat and Mark Gatiss' Sherlock, Stephanie Hyam was John Watson's maid, Jane, in the Christmas special The Abominable Bride.
Hyam expressed in a video interview that working on Doctor Who has been her favourite job so far, and that she had a lot of fun playing the villain of the episode, and interacting with Daleks.