Lord Ted Willis originally conceived Mrs Thursday as a one season retirement swan song for Kathleen Harrison, but the show became one of the top rated of 1966 leading to two more seasons and Kathleen Harrison herself being kept busy for the next decade.
ATV were so pleased with Mrs. Thursday that they offered the production team the budget for a 90 minute version but was ultimately never taken up simply because Kathleen Harrison was stunned and baffled by the adulation and lack of privacy the series had brought her and wanted to retreat quietly back into relative obscurity. However because of the series popularity in Germany Ted Willis wrote a special for German TV featuring Inge Meysel as Mrs Thursday.