How many times have we as British reenactors been asked "where's your British accent"? Paired with our habit for 20th century anachronistic phrasings, the lack of an obvious accent surely takes tourists "out of the moment" of living history. Orders shouted within British units, using our distinct American accents, surely can't be historically correct….
or could they?….
To explore the issue a little deeper, let's first consider what we Americans consider to be the proper British accent. It's actually called "Received Pronunciation" (RP), with received meaning in this case, "accepted". It can also be referred to as "BBC English" for its standard use in the mid 20th century broadcasting, or the "Queen's English" (even though this is technically a reference to dialect and grammar and not pronunciation).
The truth is that only about 2-3% of modern British people speak RP. So aside from our standard mustache-twirling villains of shows like Turn, it's very rare outside of refined circles.
I'll be the first to admit that I'm not an accent expert, and won't pretend to guess if the British officers in Turn are speaking with a pure RP accent or with a mixed accent that incorporates their own local backgrounds. But it's certainly easy to tell the difference between Turn's RP and an American accent. One key aspect, the pronunciation of the "r". Rhotic accents (ex: modern American) pronounce it, and non-rhotic (ex: most modern English, especially from the south of England) do not.
Here's the problem, though. Most scholars believe that the standard English accent of the 18th century (if a "standard" accent for the language existed at the time) was rhotic. This means that 18th century English may have had more in common with the modern American standard accent than with the modern English accent!
So what did English used to sound like? Let's take a little trip back in time - a bit further back than the Brigade of Guards - all the way back to early 17th century. The following clip from Open University is a great example of what experts think a rhotic English accent of roughly four hundred years ago would have sounded like.
So it's fairly obvious that when speaking English in 17th century London, the "r" was most definitely pronounced. But what of the late 18th century, the time period portrayed by the Brigade of Guards?
Well, that's where things start getting interesting. Even in 1757, RP wasn't around when Dr. Johnson wrote his A Dictionary of the English Language (although he did acknowledge there was a wide range of existing accents at the time). In 1780, English writer Thomas Sheridan remarked that the /r/ "always has the same sound, but is never silent." It wasn't until the 1790s that things really seemed to have changed. In fact, Americans returning to England after the War for Independence were reportedly surprised by the changes in fashionable pronunciation. By the early 1800s, John Walker, in his Principles of English Pronunciation noted how the times were changing when he commented that:
[R] is never silent…In England [R] is never silent … In England, and particularly in London, the r in lard, bard, card, regard, etc. is pronounced so much in the throat as to be little more than the middle or Italian a, lengthened into laad, baad, caad, regaad … if this letter is too forcibly pronounced in Ireland, it is often too feebly sounded in England, and particularly in London, where it is sometimes entirely sunk …
Sheridan's remarks seemed to imply that non-rhoticity was undesirable at the time, but nonetheless it soon became the norm. This might make sense because linguists believe it may have originated from the East Midlands before traveling down to London and gaining traction there. At some point, this burgeoning trend to drop the "r" became the fashion rather than the faux-pas. Therefore, linguistically, one could say that RP developed from a changing London accent that incorporated elements from the East Midlands, Middlesex, and Essex.
RP then really came into its own in the 19th century as a socially exclusive accent being taught in elite boarding schools and at Oxford and Cambridge. The actual term for RP was coined in 1869, and it received wide recognition in 1924 when Daniel Jones adopted it in his second edition of the English Pronouncing Dictionary. Two years previously, though, the BBC adopted it as their broadcasting standard.
Indeed, one school of thought holds that the accents of America, Australia, and Canada are "snapshots" in time for an evolving English dialect. Sure, each went on to develop their own regional accents and dialects, but their overall nature is a reflection of the point in time they left the "mothership" of jolly old England. For Americans, we retained the generally rhotic accent of pre-Revolution, while Australians (who were colonized after the accent shift to non-rhotic) generally do not. And Canadians, well, they're somewhere in the middle of it all.
As for us in the 4th Coy - we like the put on a show as much as the next King's man, but let's not sweat our R's too much...
Fisher, John Hurt (2001). "British and American, Continuity and Divergence". In Algeo, John. The Cambridge History of the English Language, Volume VI: English in North America. Cambridge: Cambridge University Press. pp. 59–85.
Crystal, David (2005), The Stories of English, Penguin