But, let me say again, they are likely to mind it only in somebody they think knows the rules.

With those who don't know them it is different.

I say this with all the more certainty because of a fairly recent afternoon spent in an English garden with English friends.
The question of pronunciation came up.

Now you will readily see that with them and their compactness, their great public schools, their two great Universities, and their great London, the one eternal focus of them all, both the chance of diversity in social customs and the tolerance of it must be far less than in our huge unfocused country.
With us, Boston, New York, Philadelphia, Chicago, San Francisco, is each a centre.

Here you can pronounce the word calm, for example, in one way or another, and it merely indicates where you come from.