Caroline Quentin was Renwick's first choice for Maddy Magellan, but the casting of Creek proved something of a problem. Renwick had wanted Nicholas Lyndhurst, but he turned it down. Rik Mayall was also offered the part, but was, at the time, busy with stage work (he would later guest-star in a Christmas special of the series). Hugh Laurie showed a great deal of interest and agreed to take the part, but later turned it down as he could not figure out Creek's motivations for investigating the cases Maddy involves him in, especially when he shows so much reluctance in some of the episodes.