Brown Windsor soup is a hearty British soup that is said to have been popular during the Victorian and Edwardian eras.[1]
It was one of the starter dishes on the menu at the fictional Fawlty Towers
It is unclear whether this often-written-about soup is indeed Victorian, or was invented as a joke in the 1950's - perhaps conflating the well-known White Windsor Soup with the equally famous Brown Windsor Soap. There do not appear to be any references to it before about 1953.
https://en.wikipedia.org/w/index.php?title=Windsor_soup&oldi...
Edit. The current version says:
> Windsor soup or Brown Windsor soup is a British soup that was popular during the Victorian and Edwardian eras.[1][2][3] The practice of calling it 'Brown Windsor' did not emerge until at least the 1920s, and was usually associated with low-quality brown soup of uncertain ingredients. Although originally an elegant recipe among famous chefs of the 19th century, the 'Brown Windsor' variety became an institutional gruel that gained a reputation as indicative of bad English food during the mid-20th century and a later source of jokes, myths and legends.
So, given that the author of the article "tried to update it" I don't know what they were trying to update it to?