Career
She is seen in an episode of Scariest Places on Earth as a student who had an encounter with a ghost. Her breakthrough came in 2001 with her role in the Johnny Vaughan vehicle 'Orrible. She was later chosen to play Gwen, a young woman who would later become Queen Guinevere, in the BBC One fantasy TV series Merlin. Coulby stars alongside fellow young actors Colin Morgan, Bradley James and Katie McGrath as well as seasoned veterans Anthony Head and Richard Wilson. In an interview, Coulby stated that she enjoys being able to play the character from Gwen the humble, lowly maid servant all the way to Queen Guinevere of Camelot. In that capacity, she has now starred in all the five seasons, and most of the episodes, right up to the final one.
She took the star role of the jazz singer Jessie in the BBC Two Stephen Poliakoff five-part 2013 drama serial Dancing on the Edge along with Chiwetel Ejiofor, Anthony Head, John Goodman, and Jane Asher.