From today's email:

TA note -- I've often heard people talk about pirates' "cockney accents."
Wrong! The stereotypical pirate has a Cornish accent, based on the
performance of Long John Silver by actor Robert Newton in the 1950 Disney
version of "Treasure Island". He was from Cornwall, and his over-the-top
performance and native accent are the reason people think that's what a
pirate sounded like. Of course, pirates came from all nationalities. But
the pop culture image is firmly embedded, and Robert Newton is the reason
why.

If this is true, it must mean that in Cornwall everyone talks like a pirate all the time.