Law & Order veteran Sam Waterston has booked his first post-L&O series regular role: a supporting part in the Aaron Sorkin’s drama pilot for HBO tentatively titled More As This Story Develops. The project centers on cable news anchor Will McCallister (Jeff Daniels), who has his own show, as well as the show’s female executive producer and staff. Emily Mortimer is yet to close her deal for the female lead of the executive producer, MacKenzie. Waterston will play Charles Skinner, the president of the cable news division and Will’s immediate superior who hired MacKenzie behind Will’s back. In addition to Daniels, Waterston joins recently cast Olivia Munn and Alison Pill.