It was first announced on 23 October 2004 that Robert Powell had been cast in the role of Mark. A "Holby City" spokesperson commented: "We are very excited about having Robert on board." Having signed a contract to appear in the show for at least a year, Robert Powell spoke of his introductory storyline with enthusiasm, stating that "With three Williamses on the ward, it'll be fireworks galore!" Tina Hobley agreed that his introductory storyline was "very good", adding "Robert Powell is a great actor and I am proud to be working with him."