Speaking of bunging on accents and (in the other threads) Star Wars…
In The Force Awakens, Daisy Ridley used her normal British accent, which is pretty close to RP, a bit Estuary-ish I suppose. John Boyega was made to use an American accent. Boyega’s real accent is basically Cockney: glottal stops and vocalisation of dark L (but no TH-fronting). He has said in a Graham Norton interview that he initially used his own accent but was told it was not going to work. The thing is, Boyega is an impressionist: I’m sure if he wanted to, he could use a more upscale British accent.
In any case, some folks have interpreted this choice as a message from Lucasfilm that Ridley’s character is descended from other British sounding force-users, Obi-wan Kenobi and/or Emperor Palpatine. Fans can be a bit thirsty.
Battlestar Galactica reboot that he had all the actors use their native accents
That was an interesting choice.
When you’re protraying a non-English speaking historical figure in the English language, you can either use a foreign accent (which can seem hammy) or use a “neutral” accent, which today seems to mean either RP or General American. No one seems to mind when a Soviet submariner sounds like he is from Ohio or Surrey, but if he sounds Scottish, it suddenly doesn’t make sense to people. Some critics thought that it made no sense that the Aztec Chel in Road To El Dorado had Rosie Perez’s a Hispanic accent ... but no one was troubled by the fact that the Spanish guys sounded like Branagh and Klein.
Similar choices apply when dealing with sci-fi set in the far future (or, in some unexplained way, long ago), or among people who ain’t people.Normally they’ll be given RP or GA accents, or some made up alien accent.
Temuera Morrison and Daniel Logan used their New Zealand accents when playing Jango Fett and Boba Fett, respectively, in Star Wars Episode II: Attack of the Clones. George Lucas got Temuera to revoice Boba Fett in the later remastered releases of the Empire Strikes Back in order to maintain continuity. Not everyone was happy.
Edit: finished sentence