Since series 12, there has been a head writer for the series. Prior to the introduction of a head writer, the script editor performed similar duties. Sharon Miller served as head writer from series 12–16 and stepped down after series 16 and was replaced by Andrew Brenner, who had written many "Thomas" stories for various magazines as well as his own original stories, several of which were later adapted for television episodes for Series 3 and Series 5, for which he had remained uncredited. Brenner had been a writer of several other children's animated series, such as Angelina Ballerina, Tractor Tom, Fireman Sam, The Amazing Adrenalini Brothers, Spot, Poppy Cat, and Binka, as well as being the creator of Caribou Kitchen, and Humf and writer for several magazines featuring children's characters such as The Real Ghostbusters, Fireman Sam, Scooby-Doo, Tom and Jerry, and Thomas's sister series Tugs and has written scripts and took over as head writer for Thomas for King of the Railway and onwards. Sharon Miller has also been the voice director since the second CGI animated film Misty Island Rescue, and continues to work on the series in this capacity.