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In our opinion, the most obvious choice for the part. As one of the Crawley sisters, Laura was at the forefront of 'Downton Abbey', which made a huge splash in the US, so we know she can pull off regal with ease.
Plus, after playing the oft-downtrodden Lady Edith in 'Downton', we'd love to see Laura playing a part with a bit more edge.
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Ryan Murphy is not someone who's afraid of recycling casts, with Emma Roberts starring in two different series of 'American Horror Story', before landing the lead in 'Scream Queens'.
If he were to keep one of his regulars around to play Diana, we could easily imagine it being Emma, depending on her ability to convincingly pull off a British accent.
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Then again, if Ryan were to stick with one of his regulars, the chances are it'd be Sarah Paulson, who has starred in all six series of 'American Horror Story', and just won an Emmy for her performance in 'The People vs. OJ Simpson'.
As the series have rolled on, she's been able to convincingly portray a huge range of characters on 'AHS', from two-headed Siamese twins to a junkie ghost, so Diana would probably be a walk in the park.
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Her performances in 'Happy Valley', 'Mr Selfridge' and 'The Night Manager' have proved Katherine has the skill to pull off a serious role.
Let's not forget, though, she got her big break playing the outrageous Becky McDonald in 'Coronation Street' in her, so we know she'd be able to bring some edge to the role of Diana too.
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A British star whose role in 'Girls' has helped her achieve great success international, Jemima's presence in 'Feud' would certainly bring in the viewers.
And now 'Girls' is over, we know she's got a gap in her schedule...
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Glancing through her most recent film credits, Felicity has made the jump from serious biopic to conspiracy-fuelled drama to sci-fi extravaganza, proving if nothing else she's got the versatility needed for a complex role like Diana.
She's also no stranger to the small screen, with appearances in 'Doctor Who', 'Girls' and, yes, 'The Worst Witch' all on her CV.
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"And the Emmy goes to... Chloe Jasmine," certainly has a ring to it, doesn't it?
Seriously, though. She's dramatic. She's loads of fun. And Ryan Murphy would save a shedload on voice coaching.
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Lady Gaga has proved her acting chops thanks to her roles in the past two series of 'American Horror Story', and it's expected she'll return for the seventh later this year.
She's also expressed interest in Diana in the past, name-checking her on songs like 'Dance In The Dark' and 'Princess Die'.
Here she is with Camilla Parker-Bowles... just because.
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Her roles in 'Doctor Who', 'Penny Dreadful' and 'Secret Diary Of A Call Girl' mean that she has a select fanbase overseas, while still low-key enough in the US that their prejudgements would stop them seeing her as Diana.
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How do you top a role like dragon queen Daenerys Targaryen? Why, with a role like Lady Diana Spencer, of course.
Katya's portayal of Princess Diana in the 'Baddest Bitches In Herstory Challenge' during the second series of 'RuPaul's Drag Race All Stars' left little to be desired.
This could be a chance to redeem herself, and it'd certainly be some shock casting.
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Then again, a British star known for her tumultuous relationship? Someone get Stephanie Davis's people on the phone, stat.