Originally, it was intended to make the series in colour after the pilot was filmed that way. Industrial union action caused budget restrictions, and this plan was canceled.
The series lost audience momentum in the UK as transmissions halted due to running out of episodes because of the previous union action, when it returned it was in a different slot in the summer season.
The strike was also the reason why this series - originally planned as a 26 part run - lost six editions, leaving it at only 20.
The episode The Sentimental Agent (1962) proved so well received internally at ITC that it was decided to run off a sequel series, also called The Sentimental Agent (1963).