The tendency of English characters in American works to speak with upper-class accents (the academic term is Received Pronunciation; more colloquially, it's called the Queen's English or BBC English) even when played by actual Brits, who may well "posh up" their accent. It's a case of Britain Is Only London but even more so. It's like Britain Is Only Mayfair (a very high-class area of London).
This trope is about Hollywood thinking RP is the onlyBritish Accent, or that it's the only one the educated English use while everyone else talks like they had a Cockney jammed down their throats.
To contrast, the trope is often lamented by the English who speak one of myriad other accents available and rarely get recognition, and can fuel stereotypes and people assuming there's a (nonexistent) 'British Accent'. As the page quote suggests, this might stem largely from the fact that many people think any 'non-rhotic' accent (where the 'r' is pronounced 'aa' as opposed to 'arr' in words like car and guard) is English (Estuary accent, as a result, is often confused with RP itself). In reality, both the UK and the USA have their fair share of both rhotic and non-rhotic accents to go around.
On the other hand, this trope is heavily justified in England itself. If someone mentions a "correct" pronunciation or if they have "no accent", they do mean RP, which is both relatively "posh" and the formal "standard", also known as "Newsreader English". This is similar to how Americans say they have "no accent" when they are actually referring to Lower Midwestern US pronunciation. Only so long ago, people paid for "elocution" lessons to learn to speak "properly", and actors from all over the UK were encouraged to lose their natural regional accents in favour of RP - for example, Patrick Stewart is a Yorkshireman by birth, but speaks like, well, Patrick Stewart. It should be mentioned, though, that modern RP is significantly less posh than the standard 'English' accent you will hear on American TV. The accent in question tends to be tied to a Private or Grammar School education, and it is entirely possible to identify students of particular schools in a city or region by their pronunciation.
A Running Gag among Britons (and somewhat Truth in Television) is that Americans will always assume any British accent other than the posh 1950s one is Australiannote And to add to the confusion, a posh Australian accent sounds very similar to a posh English one.. Somewhat forgiveable with Estuary English, but completely bizarre when applied to Oop North. Referenced in, among other things, Top Gear. The Quintessential British Gentleman probably speaks this way.
Also consider that Europeans often learn this variety in school, especially at university, where RP is the standard. In other countries, like in Latin American ones, for obvious reasons, learn American English, and others, like those from the Sinosphere (China, Japan, South Korea, etc.) can't decide which one is the right one to teach. Interestingly, American English is more popular in Israel despite (or maybe because of) the British Mandate.
Yu-Gi-Oh! The Abridged Series (made and voice-acted by a Brit) parodies it to hell and back by giving him lines like "Cor blimey! That was a smashing manoeuvre! Good show, chaps!" and "Lashings of hot ginger beer for everyone! ...I'm British, you know."
Surfaces in the original dub of Sailor Moon as the accent used by Minako when speaking English. Justified as, in the anime, she did live in London for a while...
Astérix and the Britons has every single Briton talk like this, complete with expressions like "goodness gracious", "jolly good fellow" and "Stiff Upper Lip". This is particularly notable in the English translation, to distinguish them from the Gauls. (In the original French version, much of the distinction is created by having them speak French with English syntax.)
Keira Knightley in most of her movies. Not so much in Real Life. This makes it extremely jarring to hear her speak in an interview for the first time.
Inglourious Basterds example: when Hicox is getting briefed for his mission, they all sound so English it hurts. Then you suddenly recognize Dr. Evil talking, and you realize that everyone in the room is a Fake Brit. Sort of Truth in Television — there are still people in the UK who talk that way, they're just few and far between (see Stephen Fry for a famous example outside the Royal Family). Fifty years ago, even more people talked like that, and whilst the common soldier would sound far more ordinary, the top brass would be more likely to be made up of the upper classes.
As was pointed out in an episode of QI, the classical English pilot of the movies talks in this fashion because the actors who played them were almost invariably upper class fellows like David Niven. In Real Life, the RAF of World War II drew most of their pilots from the middle and lower classes, but ask anyone to do an impression of an RAF pilot and they're practically guaranteed to attempt a Received Pronunciation "Tally-ho." 1/6 of the RAF's actual pilots were from the British Commonwealth (including India) and occupied and neutral countries such as Poland and Ireland (respectively) and so would have sounded (GASP) foreign.
The first half of Oliver!, where the difference is made stronger due to a juxtaposition of 'proper' and Cockney.
Richard E. Grant's super-posh accent in most of his films (e.g. as Withnail) stems from his childhood in colonial Swaziland speaking exaggeratedly upper-class "period English," overlaid with drama-school RP.
Field Marshall Bernard "Monty" Montgomery in Patton. Patton even mockingly imitates him in one scene.
Chris Egan's ridiculously poshed-up accent in Letters To Juliet (Egan is Australian by the way). Even more noticeable when he's speaking with Vanessa Redgrave, whose accent is clearly what he was going for but doesn't quite make it.
William Moseley in Walden Media's The Chronicles of Narnia films speaks on a completely different level of English-ness than his fellow cast members (including his own siblings). With his few lines in Voyage of the Dawn Treader he still manages to out-Brit the rest of the cast.
Funnily enough Richard Dempsey who played the same character in the BBC adaptations of the books did exactly the same thing.
English actor Burn Gorman does such a terrible attempt at a "British" accent in Pacific Rim, to contrast, listen to his normal accent playing Owen in Torchwood.
One of character actor Terry-Thomas' trademarks was his very British RP accent. He is quite possibly the trope codifier; most people that pretend a RP accent these days are doing an impression of him.
X-Men: First Class attempts to explain why Xavier (who is American in the comics) has a Received Pronunciation accent. He is half-British, half-American (or alternately, he's fully British, but his family moved to the United States before World War II broke out in 1939), and his speech pattern was influenced by his posh English mother. It was later reinforced when he studied at the University of Oxford.
Redwall uses a wide variety of accents: searats Talk Like a Pirate and hares use the "tally ho, wot wot"-type of speech (based on the WW2 RAF no less).
In the Doctor Who|Expanded Universe book "The Pirate Loop" the Doctor and Martha meet a group of Badger-headed pirates, most of whom speak in an English -specifically Southampton- accent.
Live Action TV
Dollhouse: The Trope Namer is Adele DeWitt, who is played by English actress Olivia Williams, but with a poshed-up accent. Under the influence of a drug, she says "Still you have to admit, I am... very British.".
Averted with Daphne in Frasier, who speaks with a Mancunian accent. Or rather, what is supposed to be a Mancunian accent. Averted with almost every English character in Frasier, though Daphne's family suffer a greater accent-drift than she does, making you wonder if they're doing it on purpose.
Alias has the suave terrorist Sark, a young English gentlemen who's insanely cool under pressure, always polite and always has an English quip ready at any time. And unlike most examples on this page portrayed by non-English actors, David Anders nails the accent to the point where he even fooled native ears.
Buffy: Giles and Wesley and well pretty much any watcher really. Also found in Angel. At least for Giles, it's eventually made clear that the accent is something of a put-on for the character as well as the actor. Wesley's accent, however, gets less posh the more time he spends in America and he is able to gradually phase out what Americans expect to here of an English accent.
Band Candy shows that Giles' real accent is similar (though exaggerated) to his actor's real accent. He just does the more posh one to fit in more with the other Watchers and distance himself from his dodgy past.
Even vampires such as Spike (or Spoik) and Drusilla play up to stereotypes with their silly accents terribly done. But because they are basically Victorian nutters, it works.
Much like Giles, Spike's accent is shown in a flashback to be entirely fake and that he had a different accent (also English, but much different and somewhat more realistic) before he decided to use the one he currently uses to sound more badass. James Marsters (Spike) actually based it on the real accent of Anthony Stewart Head (Giles). It is terrible, as is Drusilla's.
Spike's kind of the reverse of Giles. Giles has, depending on interpretation, either poshed-up his accent to fit in as a Watcher or *reverted* to posh after affecting a lower-class accent in his rebellious youth. Spike started out posh, but has deliberately moved his accent downmarket and stayed there. Then there's Drusilla, whose strangled Cockney tones ARE supposed to be her natural accent, but who put on a posh one when she first met human-Spike, presumably to put him at ease: ironically, this "fake" accent is far more convincing than her "real" Cockney one. Yet both are awful to the true English ear.
The Watchers Council being entirely full of posh dudes in tweed who speak like some variation upon Rex Harrison. Even the surly 'lower class' henchmen have this ludicrous 'pip pip cheerio God Save the Queen!' dialogue.
Depends also on the writer - some simply write amusing scenarios and get the actors to flesh it out. Joss Whedon went to a renowned English independent school so has direct experience of such prim, tweedy characters. Others (such as Jane Espenson in particular) attempt to introduce British "slang" and end up sounded daft because they are unfamiliar with this type of dialogue.
Averted for all of roughly two seconds in "Hush" with Giles' Liverpudlian girlfriend Olivia.
Firefly: In another Joss Whedon show, the only British people there speak in a Cockney accent. One episode involves River Tam faking it really, really badly. Seeing as she's a Cloud Cuckoo Lander, however, this could very well be in character.
In yet another Joss Whedon-produced show, Agents of S.H.I.E.L.D. both averts this trope and plays it straight with the two British leads: Fitz is played by a Glaswegian actor with a moderately strong Scottish accent, while Simmons speaks in the more typical RP of a British character in a US show, despite the actress playing her originating from Sheffield. In later episodes this trope begins to be averted a little with Simmons too, whose Southern-ish RP accent slips gradually towards more Northern English pronunciation (which seems to be her real accent, to judge from interviews). This is particularly the case when she's speaking quickly or with high emotion, but is increasingly just used for the character's ordinary conversation.
Also Dr Helen Magnus from Sanctuary. Justified because she is very old so it's her real accent, not a put-on.
Marcus from Babylon 5, in an attempt to sound Arthurian.
In one episode of Murder, She Wrote we have a father-daughter pair where the daughter is a social-climbing gold digger who has taught herself to speak like a lady, where the father still speaks like a workingman.
Wee Britain in Arrested Development is an entire neighborhood of Very British People, with the only possible exception being Rita's uncle, who is played by a Canadian and sounds more Australian than British. Theron as Rita's attempt at an English accent are cringeworthy.
One story arc involves Tobias pretending to be a British nanny (the characters and narrator all lampshade the fact that it's a blatant rip-off of Mrs. Doubtfire). His accent and attempt at slang are terrible. However, this fits in with the rest of his Paper-Thin Disguise; all the other characters immediately know it's Tobias and only pretend to be convinced so he'll do their chores.
A new arrival in Colditz is suspected of being a spy precisely because he's such a stereotype. Nope, he's just really, really posh.
Pat: I didn't realise anyone was that English these days. Player: You don't think he's... too English, do you? [...] Seems to me he's a German's idea of what an Englishman looks like.
Top Gear: As mentioned above, during their visit to Reno a couple of drunken casino-goers "helping" James May with a slot machine ask him if he's Australian because of his accent. Then again, they are very drunk, since one of them also asks him if he's John Lennon.
An episode of Friends has Monica and Phoebe getting annoyed when a friend of theirs returns from living in England with a "ridiculously fake British accent". Their attempts to imitate her result in this trope. Ironically when the friend actually appears, her accent is quite decent.
DI Richard Poole in Death in Paradise speaks with a Received Pronunciation accent that marks him as wildly out-of-place on the Caribbean island where the show is set. None of the other British characters speak like this, so it seems to be Poole's natural way of speaking, which fits with his very proper and straight-laced personality.
Averted with Alfred Pennyworth in Gotham, who speaks with an East London Cockney accent instead of the Received Pronunciation heard in most adaptations.
Katarina Waters aka Katie Lea Burchill/Winter has an RP accent but did posh herself up considerably when she was in WWE and then again in TNA. Any non-kayfabe interviews will show a big difference between her real accent and the one she uses in promos. Possibly justified because in professional wrestling, the wrestlers are taught to speak slowly in promos and enunciate so that the audience can hear them clearly.
Katie Lea's "real" accent is actually very Germanic, as she was raised in Germany. In a Colt Cabana podcast she relates that to English ears she sounds German but she gets away with it in America.
William Regal poshed up his Lancashire accent when he was first in WWE as his character was meant to be a proper British upper class twit and would naturally have a posh accent. He dropped this around 2004-ish and has used his normal accent ever since.
Booker T and Sharmell gave themselves over the top British accents when they became King Booker and Queen Sharmell and started acting like bumbling upper class twits.
Layla El is British but has lived in America for a long time so her accent has faded quite a bit but she did posh herself up when she hooked up with William Regal as his "Queen". She did a similar thing when she formed Lay Cool as a listen to one of her promos from then and a regular interview will show a huge difference.
Metal Gear usually plays this straight where English characters have English accents, with varying levels of justification. Major Zero is an ex-SAS man from Exeter and Liquid Snake is... well, LiquidSnake. Slightly less justified is the supposedly Mancunian Strangelove. The only exception is the Praying Mantis advert narrator.
The Icarus from Sacrifice is an obvious 'stereotypical RAF pilot' reference and speaks in an extremely posh upper class accent (in contrast to the rest of the Yeomen, who mostly speak with various lower-class accents from both Britain and the USA).
South Park - Zig-Zagging Trope - First, Pip has this accent. In "The Snuke," the Queen has one too, but her underlings don't. They also give Gordon Brown a London accent that sounds a bit like their version of Russell Crowe even though Brown has a fairly pronounced Glaswegian (i.e. 'Scots', think Billy Connoly) accent. Finally, they don't give Richard Dawkins this accent even though he does have one. (When asked about his portrayal in Real Life, Dawkins responded that they could have at least hired an actual British actor.)
On Phineas and Ferb Lawrence Fletcher, the dad, has this, but Ferb seems not to, though as a child that has spent his formative years in the United States he can reasonably not have one.
In an episode of Pinky and the Brain where Pinky assembles the world leaders, Prime Minister John Major has a stereotypical English accent instead of the South London accent he has in real life.
Thomas the Tank Engine: Extremely noticeable with Gordon in later episodes. He is even based on the same model as the Flying Scotsman, an actual steam locomotive that was manufactured in Britain.
One of the Sports Popples, Big Kick, talks with a British accent.
Isabella M: "Nothing. Everyone from London, England has to talk like this."
Inverted by George Thomas, 1st Viscount Tonypandy, who, when he was the Speaker of the House of Commons, said in his native Welsh lilt, "There are many accents in this house. I sometimes wish I had one myself."