I have just seen a statement in another blog which bluntly asserts that what the blogger calls "the rule" No Brown In Town "has pretty much no relevance in London today". In Book III I mention 'rus in urbe' and, although it is a tag that is normally applied to gardens, I recognize that there are times and places in town when a relaxed attitude might be taken over dress when out and about.
However, so far as the blogger's heedless generalization is concerned: First of all, No Brown In Town is not a general "rule" but often a carefully observed custom, in such places as certain places of work and the better clubs. Moreover, even though evening dress has disappeared as everyday wear, there are many who would take a dim view of a man pitching up to the opera (or to a funeral) in brown shoes. Sometimes, it is an actual rule (e.g. advocates appearing in a Court are still instructed to wear black shoes).
Just because the threads of our civilization are being unravelled by barbarians and its remaining customs are being rent asunder by just about all those who can grab a a corner of them, are not reasons to hasten the process with gratuitous exhortations to destroy perfectly reasonable, established customs on the (implied) false premise that they are oppressive "rules" imposed by an overtaken elite, whose customs are being disregarded in the free-fall, free-for-all scrum of The Common Man in modern Britain; which, incidentally, Blair, Garden Broom and Mandy did not invent; as Thatcher laid the foundations for the rot setting in with her statement that "There is no such thing as Society".
The photograph is a still from the film My Fair Lady of Audrey Hepburn, Wilfred Hyde White - and Rex Harrison an example of rus in urbe but he wouldn't have been likely to get into the opera in that rig "Not in them days Guv'nor!"; even if, within the confines of the phantasy of the film, he does get into the royal enclosure at Royal Ascot, dressed in tweeds.