Embeth Davidtz is South African-American but often finds herself called on to play English characters. Partly because her natural accent isn't too different from an RP one, and she only has to change certain pronunciations. Bridget Jones, The Hole, Mansfield Park, Scrubs. The film Junebug is one of the few projects where she gets to use her natural accent - as her character is also an American who was raised in South Africa.
The most (in)famous example — cited for almost forty years now in anecdote, song and story — is Dick Van Dyke as Bert the chimney-sweep in Mary Poppins. The almost universal negative reaction to his overly fake Cockney was probably the reason that the next time he played an Englishman — Caractacus Potts in Chitty Chitty Bang Bang — he dispensed with the accent altogether. (Ironically, in Mary Poppins he also plays another Englishman, Mr. Dawes Senior, and disappears so completely into the role many viewers don't realize it's him until the final credits). This was actually a pragmatic decision. Dick van Dyke tried to do a realistic Cockney accent. And tried. And tried. And failed. And failed. Finally, he decided that since he could only do a bad Cockney accent, he'd do a hilariously bad one.
The Hollywood classic Young Bess has a mostly British cast. The lone exception is Rex Thompson, a New York native, playing the young Edward VI. Not that you'd know; his accent is very good. There's also Robert Arthur as Tom Seymour's dim-witted page Barnaby - who is just about passable.
Notably averted in The Great Muppet Caper. A particularly reckless taxi driver comments about having lived in London his whole life. When asked why he doesn't have a British accent, he nonchalantly responds that he's lucky to even have his driver's license.
In the Steve Martin movie L.A. Story, Canadian comedian/actor Rick Moranis has a cameo as an English gravedigger, with the accent made to match. His attempt sounds rather corny. In-universe, Trudi accuses Sara of this — and Sara is British!
Don Cheadle plays Basher Tarr with poor-Cockney abandon in the remake of Ocean's Eleven and its sequels, complete with jokes about its incomprehensible rhyming slang.
Basher: So unless we intend to do this job in Reno, we're in barney. (everyone looks confused) Barney Rubble. (still confused) Trouble!
Elijah Wood as Frodo, doing RP to match Ian Holm's voice as Bilbo.
With Sean Astin bringing up the rear with his portrayal of Sam having a 'country' southern English accent.
Other Americans donning fake English accents of The Lord of the Rings: Brad Dourif as Gríma Wormtongue, who never used his normal accent in order to maintain it and only stopping when filming ended, which caused Bernard Hill (King Théoden) to wonder why he was suddenly using "such a fake American accent"; and Liv Tyler as Arwen, whose voice was so low that her own father wondered who the voice actor was. And also, Viggo Mortensen as Aragorn.
Josh Hartnett's ludicrous attempt at a Yorkshire accent in the Keighley-set hairdressing comedy Blow Dry.
Renée Zellweger as Bridget Jones. Her portrayal, along with her posh English accent was widely praised. Co-star Hugh Grant allegedly believed she was English to the point of wondering why she was using a weird Southern accent when he heard her speak in her natural voice after filming had wrapped. She also donned this accent for her role as Beatrix Potter in Miss Potter.
The Queen has a cast that's almost entirely British — except for Prince Philip, played by Los Angeles-born and Manhattan-raised James Cromwell. Prince Philip himself is a naturalized Briton having had to renounce his Greek ties before he was allowed to either marry the Queen (then the princess) or be served a peace-time Naval commission.
Two of the actors who played James Bond — Pierce Brosnan is from (southern) Ireland and George Lazenby is from Australia. All the others are British, whether from Scotland (Sean Connery), Wales (Timothy Dalton) or England (Daniel Craig, Roger Moore, David Niven). On two occasions, American actors have been either cast as Bond or were expected to take the role, only to be dropped: John Gavin was signed to play Bond in Diamonds Are Forever until Connery agreed to return; James Brolin was all but signed to debut as Bond in Octopussy until Moore returned. Numerous other actors, including Americans Adam West and Burt Reynolds and Australian Sam Neill, have been considered for the role over the years, any of whom would have presumably been required to adopt a British accent for the role.
A Knight's Tale has Heath Ledger (Australian), Shannyn Sossamon (American) and Alan Tudyk (American) putting on English accents. Subverted with Laura Fraser, who got to use her natural Scottish accent as Kate - the first time she had been able to do so in a film.
Claire Danes in Stardust pulls off an English accent quite well as Yvaine— particularly given that there's no reason that a star fallen from the sky should even have a British accent to begin with. Michelle Pfeiffer as Lamia... not so much.
The Prestige features a few fake Brits in the main cast. Hugh Jackman turns out to be playing a Brit, pretending to be an American. Scarlett Johansson adopts a lower class cockney accent that varies in consistency. Piper Perabo meanwhile does a very good job as Angier's wife Julia.
In the film Bram Stoker's Dracula, Keanu Reeves, Winona Ryder and Tom Waits all play English characters in Victorian London. Keanu Reeves's is suitably terrible (and he himself has apologised for it in interviews), Winona Ryder's is quite decent and Tom Waits's is good.
Imagine Me & You features Piper Perabo sporting an unconvincing British accent, but she had perfected it by the time of The Prestige mentioned above.
One Day features Patricia Clarkson playing the English mother of Jim Sturgess. She holds up a little better than Anne Hathaway.
The made-for-TV movie Sherlock: Case of Evil cast New York native Vincent D'Onofrio as Holmes' nemesis Professor Moriarty with an accent that's just plain embarrassing.
American Michelle Williams sounded very natural in the part of Holly in film Me Without You playing opposite Anna Friel (who is English, from Greater Manchester) as they both play southerners (Received Pronunciation accent). In fact Williams pulls off the accent even better than Friel.
Chris Egan uses an accent somewhere between his native Australian and "posh" British in Letters to Juliet.
There's Something About Mary has an in-universe example. Tucker, Mary's 'English' architect "friend", is revealed to be an American pizza delivery boy named Norm. His actor, comedian Lee Evans, is British. So he's a Brit pretending to be an American pretending to be a Brit.
The Rocker has a scene at the end where after finally confronting Vesuvius, Fish realizes they all have British accents now. They all deny ever having been American. Later on in the scene the person who replaced Fish points out to him that he actually is British.
Nigel Tufnel and The Six-Fingered Man? Both played by the same American, Christopher Guest. Although, Guest's father was British - a hereditary peer, in fact, as he himself is now - which may have influenced him. He's not perfect though.
An in-universe example in Just Go with It, where Katherine's daughter is an aspiring actress who insists on speaking with a terrible English accent (the "'ello guv'nah" kind). They are forced to make up a story for Palmer where the daughter was in a British boarding school for a few years.
My Fair Lady contains the interesting idea of casting Audrey Hepburn as Eliza Doolittle - a character whose entire plot is based around her cockney-RP dialect shift. An interesting casting choice, that. Mind you, squire, she din't do an arf bad job. While the woman singer dubbing Audrey as Eliza sounded acceptably English, the man dubbing Jeremy Brett as Freddy unfortunately sounded North American.
American actress Julianne Moore's character in A Single Man. Apparently Moore listened to early Julie Christie for the sixties feel and mixed it up with modern British party girls to get her character's way of speaking. Moore also did an excellent job of a 1940s upper middle class Englishwoman in The End of the Affair.
Selena Gomez in Monte Carlo as two separate characters. The first; her portrayal of the fictional English heiress Cordelia Winthrop-Scott and then her portrayal of an Identical Stranger from Texas, Grace, posing as Cordelia. Grace's fake accent is not entirely convincing, but that's kinda the point; Cordelia's accent is a bit better but that might just be because she had fewer lines.
Americans Edward Norton and Liev Schreiber play nineteenth-century English gentlemen in the 2006 adaptation of The Painted Veil. The accents are pretty good. They at least avoid sticking out compared to Australian/Brit Naomi Watts.
In Hugo - set in Paris, but everyone speaks with a British accent - American Chloë Moretz pulls this off impeccably.
Bette Davis in the film adaptation of Of Human Bondage. She is said to have hired a British maid just to help her learn the accent. It varies in consistency. She always said Mildred's voice was particularly tricky, describing her as someone who tried to sound higher class than she actually was.
Prometheus stars Swede Noomi Rapace as the English Elizabeth Shaw. Her native accent trickles through quite a bit. Her father is also played by the American Patrick Wilson.
An In-Universe example in The Sting. Curly Jackson, a grifter from Baltimore who joins the con, likes to masquerade as an Englishman.
In the 1998 glam rock opus Velvet Goldmine, the Irish Jonathan Rhys Meyers played a glittering bisexual English rock star (a David Bowie expy, in fact) rather well. On the flip side, the very Scottish Ewan McGregor faked it up really well as a big, bombastic, showy American rocker (an Iggy Pop expy) in the same film.
In the 2005 film The Best Man American Seth Green plays a Londoner. Those in the know say it's pretty much spot-on for a character of that particular demographic, only slipping up when he gets excited.
South African Alice Krige specialized in this (except her most famous role as The Borg Queen).
The 1964 AIP Bikini Beach features Frankie Avalon as his usual self and as British pop star Potato Bug. The Beatles were just new and foreign enough then for him to play the part like Terry-Thomas on amphetamines.
American actress Alison Brie as Suzy in The Five-Year Engagement, which was a spur-of-the-moment thing. Emily Blunt plays her sister and keeps her natural accent, so Alison does an imitation of Emily's. She apparently fooled Judd Apatow into thinking she was British.
American Lake Bell plays English woman Nancy in Man Up, a film set in the UK.
In Noah despite being set in Biblical times, the cast speak with English accents. Brits Ray Winston, Emma Watson and Douglas Booth use their natural voices, while Americans Logan Lerman, Madison Davenport and Jennifer Connelly and New Zealander Russell Crowe all affect English-sounding accents.
Naomi Watts is British born but grew up in Australia and has that accent. She has played British characters in The Impossible and Diana.
The 2001 thriller The Hole has a mostly British cast. The exception is American Thora Birch, who does a passable attempt at an English accent.
Elle Fanning as Princess Aurora. She leans more towards the I Am Very British school, though some viewers mistook her accent for Scottishnote Her father Stefan has a Scottish accent but she's raised by Maleficent and the three pixies who have English.
Aussie Brenton Thwaites also affects an English accent for his small role as Prince Philip.
A Royal Night Out has only one of the three leads played by an actual Brit. Canadian actress Sarah Gadon does a very convincing imitation of Queen Elizabeth's voice. Irish actor Jack Reynor nails a 1940s cockney accent as Jack.
Snow White and the Huntsman features Kristen Stewart putting on a quite decent accent to play the titular princess. Charlize Theron does likewise to play Ravenna. Most of the supporting cast are British though.
In the Harry Potter film adaptations, this is averted for the most part. JK Rowling insisted that the cast and crew had to be British - as there were talks of Haley Joel Osment starring as Harry. Zoe Wanamaker is American born but grew up in Britain, and so does not have to fake an accent. Eleanor Columbus, daughter of the director Chris Columbus, is a featured extra as Susan Bones - but has no lines. Verne Troyer, who plays Griphook in the first film, is American but has his voice dubbed by Warwick Davis. Scottish actress Kelly Macdonald affects an English accent to play Helena Ravenclaw. They're less strict about it with the prequel film series, Fantastic Beasts, as American Zoë Kravitz has a prominent role as Leta Lestrange who was born in France and raised in the UK.
Sleepy Hollow (1999) is set in 18th century America, but many characters have English accents presumably to reflect that the American accent had not yet fully developed. It stars the aforementioned Johnny Depp. American Christina Ricci puts on an English accent to play Katrina, as does Irish actor Michael Gambon. Ironically the British actress Miranda Richardson puts on an American accent to play Lady Van Tassell. The rest of the cast use their own accents.
Ever After, despite being set in France, has a cast full of actors faking English accents; Americans Drew Barrymore, Anjelica Huston, and Megan Dodds, New Zealander Melanie Lynskey and Scottish Dougray Scott.
Love & Friendship, a film adaptation of Jane Austen's Lady Susan had Reginald DeCourcy played by Australian actor Xavier Samuel.
Bryan Cranston has a cameo in the film Leave playing a stuffy English professor.
Miss Pettigrew Lives for a Day stars the American Frances McDormand as the very English Guinevere Pettigrew. The accent holds up very well, only slipping in the scene where she finds Michael in the flat. The film has Irish actor Ciaran Hinds putting on an English accent too.
Robin Hood (2010) featured yet another non Brit as Robin - this time Russell Crowe. His poor attempt at an Oop North accent was attacked by critics and he's been known to walk out of interviews if he's ever asked about it. Most of the cast is made up of Fake Brits. The Merry Men are played by two Canadians (Kevin Durand and Alan Doyle) and an American (Scott Grimes). Swedish actor Max von Sydow plays Sir Walter Loxley, American William Hurt plays William Marshall, Guatemalan born American Oscar Isaac plays Prince John and of course the Australian Cate Blanchett as Marion. All of these accents are marginally more solid than Crowe's.
Meryl Streep has pulled off an English accent in several movies. The first one was The French Lieutenant's Woman - in which she sounds uncannily like Deborah Kerrnote This is the one performance she admits she's not proud of, ironically enough.. She's also done it in Plenty, and of course playing Margaret Thatcher in The Iron Lady.
Parodied in Hail, Caesar! when the movie studio decides to have singing cowboy Hobie Doyle star in a romantic drama - that requires a posh accent. Note that Hobie is verysouthern. His line "would that it were so simple" gets changed to the shorter "it's complicated" in the end.
Educating Rita is set in Liverpool but filmed in Ireland. Although its main cast members - Julie Walters, Michael Caine and Maureen Lipman - were British, a good amount of the supporting cast were Irish. A couple don't bother with the accents, which is justified since Britain has always had a large number of Irish immigrants.
Despite Elizabeth and its sequel being made and set in Britain, there are a few actors faking English accents:
The Irish Short FilmHigh and Tight has Irish actor Thomas Fitzgerald putting on an English accent as Ryan. He does have English roots on his father's side however.
Canadian-American Mike Myers puts on three British accents in his Austin Powers trilogy: English for Austin and Dr. Evil, and Scottish for Fat Bastard. He then adds a faux-Dutch accent in the third movie for Goldmember. In addition, his One-Scene Wonder role in Inglorious Basterds as a British general has been praised by critics.
The Constant Gardener has a mostly British cast, but Danny Huston (American) puts on a quite decent English accent to play Sandy Woodrow, the British High Commissioner.
Much publicity came from the fact that Emma Stone would be doing an English accent to play Abigail in The Favourite.