One of the primary reasons for diverging from the original books was that many of the stories not yet used featured large numbers of new characters, which would be expensive to produce. Another reason was that the producers wanted more stories about Thomas, the nominal main character. Awdry complained that the new stories would be unrealistic (see Henry the Green Engine for more details). Robert D. Cardona left as producer, while Britt Allcroft joined David Mitton as co-producer. Angus Wright took over as executive producer.