Ever since we learned that Prince Harry would be saying 'I do' to Meghan Markle at Windsor Castle on 19 May 2018, we've been busily dreaming up exactly what style of bridal gown the Suits star will choose for her big day.

After all, let's not forget that over two billion people turning into the 2011 royal wedding to catch a glimpse of Kate Middleton's wedding dress. And the fact Markle has to follow a line of famous British princesses and queens who have donned gowns designed by the likes of internationally renowned designers Sarah Burton, David Emanuel and Norman Hartnell.

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Let's just say, a last-minute ASOS buy might not do for the occasion.

As a result, we've rounded up all the details we know so far about Markle's wedding look, from her hair and nails to her designer dress and tiara:

The dress

Unlike Princess Diana and Kate Middleton who wore white gowns designed by British fashion designers, David Emmanuel and Sarah Burton for Alexander McQueen respectively, given Markle's American heritage it is widely thought she may break from tradition and choose a non-UK based designer.

For example, in Suits her character Rachel Zane donned an embroidered, plunging v-necked A-line gown by US bridal designer Anne Barge for her wedding in the finale of Season 5.

And the bride-to-be has previously revealed that she's a big fan of Paris-based designer Delphine Manivet and newcomer Greek-based artist Christos Costarellos, given 'their uniqueness and beauty'.

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She also previously told Glamour that she'd 'always be a fan of couturier Elie Saab. J.Mendel is spectacular'.

Last month, the star's BFF and French designer Roland Mouret also hinted he might have already created the dress ('She's a friend. And that's…I can't say'). But we think we can rule our Canadian designer Jason Wu who recently remained schtum when questioned for more details.

'I have no details. I think when it comes to that, I'd rather be more confidential about my clients,' he revealed to News.com.au.

And despite speculation Markle may shun British tradition and opt for a non-UK based designer to create her bridal gown, it's now being rumoured that royal favourite Erdem might be the mastermind behind the dress.

Erdem, the British fashion house run by the Canadian-born designer Erdem Moralıoğlu, just announced that they are no longer outsourcing their PR to an agency and are bringing their public relations operations in-house with the hire of a new PR manager, Kathryn Lo, according to Diary Directory.

Since Erdem is already a favourite among betters to be the royal wedding dress designer, the fact that they’re 'staffing up', as People reported, is a huge hint the brand be preparing to design the wedding dress of the year/century.

That's not to mention Erdem would create the perfect unity between Meghan's and Harry's heritages and serve a fitting tribute to the star's new home in England and her home for the last seven years, Toronto, where she filmed Suits.

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Meanwhile, in February, bookmakers Paddy Power, revealed it had received a 'flood of bets' leading the odds of Sarah Burton (creative director of Alexander McQueen) falling from 16/1 to 8/1 in one morning and down into the two's.

'Our traders have been inundated with bets for McQueen to be the designer of Meghan's dress this morning. So much so they've had to suspend the betting,' a spokesperson said. 'Either someone sneaky knows something, or there's plenty of shrewd punters who are up on their fashion knowledge.'

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The spokesperson added to ELLE UK that they do not know why the huge influx of McQueen bets happened, it could be that they are 'in the know', 'have heard a whisper', may be fashion followers or could just be guessing.

However, let's not forget Ralph & Russo, the brand who designed the black and gold gown Markle wore in her engagement photos.

The fashion house is also hiring a new PR assistant, according to a LinkedIn post.

In December, sketches from Israeli designer Inbal Dror were leaked to TMZ.

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Inbal Dror

Dror - who previously dressed Beyoncé for the Grammys in 2016 - drew up a series of designs, all involving long sleeves, a cinched in waist, and high-neck lace collars.

One design is markedly more A-line, similar to Kate's Sarah Burton for Alexander McQueen dress, while the other two have sleeker skirts to accentuate Markle's trim figure.

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Inbal Dror

On one sketch, the designer has even scribbled 'long long train' on the side, suggesting Markle might be considering bettering Princess Diana's famous 25ft train.

All three of Dror's sketches echo that of traditional royal wedding dresses seen on both Kate and Diana.

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Inbal Dror

When the Duchess of Cambridge married Prince William in April 2011, Clarence House described her bridal gown as 'epitomises timeless British craftsmanship by drawing together talented and skilled workmanship from across the United Kingdom'.

'Miss Middleton wished for her dress to combine tradition and modernity with the artistic vision that characterises Alexander McQueen's work.'

Could we be seeing a similar design in Markle's gown?

The make-up

While it's a well-known fact that Kate Middleton did her own make-up on her wedding day, we have a sneaking suspicion Markle - who is well-accustomed to being in the make-up chair on the set of Suits - might opt for professional help on her big day.

Celebrity make-up artist Min Min Ma is a long-term favourite of the 36-year-old, having previously worked with the star for multiple television and red carpet appearances.

Currently based in New York City, we would expect Min Min Ma to opt for a traditional look for the star, accentuating her nude lips with a caramel or blush pink hued stain, as well as some subtle brown, earthy eyeshadow tones to emphasise Markle's brown eyes.

Similar to her future sister-in-law, who opted for a thin line of black eyeliner on her wedding day, we suspect Markle won't deviate too far from her everyday make-up and choose a soft smokey eye for the occasion.

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When it comes to Markle's 'power' brows, all eyes are on her favourite Mayfair salon Nails & Brows to be on hand for the occasion, with founder Sherrille Riley recently revealing the actress opts for 'The Audrey' treatment with her.

The look uses a combination of waxing, tweezing and threading to create a 'modern, elegant and super flattering' style, perfect for a wedding.

The tiara

Like Kate Middleton, Meghan is now a proud owner of a piece from Princess Diana's vast jewellery collection (her engagement ring features two of the royal's stones) but what we really want to know is whether the actress will be fortunate enough to wear one of Diana's famous tiaras.

Royal expert Ingrid Seward recently revealed to US Weekly: '[Meghan] will have access to jewels from the royal collection made available to her by the Queen.

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'She can choose something suitable, but she might also have the Spencer tiara, which is also Harry's heritage and is the one Diana wore on her wedding day.'

On Kate Middleton's wedding day, the mother-of-two wore a wedding tiara with nearly 1,000 diamonds in total, initially purchased from Cartier in 1936 as an anniversary gift from King George VI to his wife. Meanwhile, Diana wore a Spencer tiara for her marriage to Prince Charles.

'If not, [Meghan] will certainly be loaned a tiara on her wedding day. Harry will present her with a necklace or something from his mother's collection.'

The nails

With all eyes on her wedding finger next May, it's no surprise Markle is hoping to achieve the most perfect look on her big day and, of course, the star's keen eye for detail and beauty doesn't stop at her hair and dress.

When it came to the Duchess of Cambridge's manicure for her wedding, OK magazine reported the bride put a request in to nail varnish giant Essie to choose a pale pink polish dubbed 'Ballet Slippers' to wear on her wedding day.

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The nail varnish hue is also a firm favourite of Queen Elizabeth II, who, according to the brand's website, once had her hairdresser send the company a letter requesting a bottle of the polish as it is 'the only colour Her Majesty would wear'.

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Essie describes the colour as a 'classic pale pink polish is graced with a subtle, sheer finish', perfect for a timeless bridal finish.

Anyone want to bet Markle might opt for 'Ballet Slippers', too?