The first of Joanna Lumley's appearances on the show. Lumley had been married to show co-creator and writer Jeremy Lloyd.
When the cleaning ladies are told to get about their business, one of them trips while exiting the scene. Mrs. Slocombe steps into the shot trying not to laugh.
"Going like a dose of salts" is a dated simile for doing something guickly and to great effect. Disturbingly, this image comes from using a dose of Epson salts as a powerful laxative.