The fourth series of the British drama series Merlin began on 1 October 2011 with the episode "The Darkest Hour - Part 1". It consists of 13 episodes originally shown on Saturday evenings on BBC One and BBC One HD (repeats shown on BBC Three). Series producer is Sara Hamill and executive producers are Johnny Capps and Julian Murphy. Directors include Alice Troughton, Alex Pillai, Justin Molotnikov and Jeremy Webb. Writers include Julian Jones (head writer), Howard Overman, Jake Michie, Lucy Watkins, and Richard McBrien.