The female Moonbase crew usually wear their purple wigs, even in the leisure sphere - except in this episode.
The character of the visually impaired actor 'Sir Esmond' played by Roland Culver, was perhaps based on real life actor Esmond Knight, who remained totally blind for two years, though later regained some sight in his right eye.
In the original concept, the character of 'Colonel Lake' was written as "2nd in Command" and Gary Raymond (Colonel John Grey) was the front runner for the part. Eventually, it was decided to make Colonel Lake a female character and Wanda Ventham won the role.
The only episode to show Colonel Lake wearing the silver jumpsuit and purple wig.