Mark Williams is a fictional character from the BBC medical drama "Holby City", portrayed by actor Robert Powell. The character first appeared in the series seven episode "Stick or Twist", broadcast on 15 February 2005. Mark was created as a new addition to the show's existing Williams family, entering as the ex-husband and father of established characters Tricia Williams (Sharon Maughan) and Chrissie Williams (Tina Hobley) respectively. Powell stated that he was looking forward to the opportunity to develop the character over a longer period of time than with the briefer acting roles he was more used to taking.