Career
Originally, she worked behind-the-scenes as a wardrobe assistant on The Tudors. She was then tapped to be an extra in one scene.
She's Irish but because she works on British TV and her accent isn't familiar outside Ireland a lot of people think she's British.
Not in real life, but her rather aristocratically pale good looks seem to make her a natural choice for such roles, to the extent that she has already played two British princesses (The Queen, Merlin) and a Viscountess.
In 2010, McGrath was cast in Madonna's directorial debut W.E., a King Edward VII biopic. It was later revealed that McGrath is to play Lady Thelma Furness, the king's former mistress who introduces him to Wallis Simpson.
In September 2011, Katie started voice recording for a character in an upcoming animated short film Trìd an Stoirm. Later that month, McGrath was cast as Oriane Congost in Labyrinth.