Nanny’s ring story is a well-known folk tale that goes back as least as far as Herodotus, but has also been used by e.g. Tolkien and Jack Vance.
More interesting is that at least one non-Brit over on alt.fan.pratchett had some trouble making sense of the implied connection between the concepts of ‘turbot’ and ‘tea’. What he did not realise was that ‘tea’ is the term the British tend to use for any meal taken between 4.30 and 7 pm, which may therefore include a nice, juicy turbot.