Page "Quotation mark" Paragraph 5

When dealing with direct speech, British placement depends on whether or not the quoted statement is complete or a fragment.

According to the British style guide Butcher's Copy-editing, American style should be used when writing fiction.

In non-fiction, some British publishers may permit placing punctuation that is not part of the person's speech inside the quotation marks but prefer that it be placed outside.

Periods and commas that part of the person's speech are permitted inside the quotation marks regardless of whether the material is fiction.