The way Meghan Markle will honour Princess Diana at her wedding

At Meghan Markle's upcoming wedding to Prince Harry on May 19, it's believed she will make a sweet tribute to Princess Diana.

Speculation about which tiara Markle will wear on the day (or indeed, whether she will wear one at all) has been building all year. But if you believe 'Royal Butler' Grant Harrold, it's now looking like a pretty sure thing that it'll be one that belonged to Harry's late mother.

"I believe she may opt for the Spencer tiara which was famously worn by Lady Diana Spencer on her wedding to Prince Charles, and on many more occasions throughout her life," Harrold told Daily Mail.

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The 1930s headpiece is reportedly now owned by Harry's uncle, Earl Spencer, so the couple would need permission to borrow it for the big day.

"This could be a way for Prince Harry to involve his mother in his big day, as Prince William did when he gave his future wife Kate Middleton his mother’s engagement ring."

WATCH: Prince Harry, the husband. (Post continues.)

We do know that Markle won't wear the same tiara Middleton did on her wedding day. That piece, a Cartier diamond tiara loaned to Middleton by the Queen, will apparently be on show in Australia at the time.

But there is another option – also a favourite of Diana's: the Cambridge Lover's Knot, originally made for Queen Mary, and given to Diana by the Queen as a wedding gift. This tiara has been worn by Middleton in the past.

Harry has already given a nod to his mother during this royal courtship. He famously designed Markle's engagement ring using diamonds from Diana's collection, and told reporters at the time he thought the pair would have been "thick as thieves" had they known each other.

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Of course, it's possible that – as she has done in so many ways – Markle will buck tradition, and go tiara-free. Whatever she decides, she and Harry are sure to have a Princess Diana tribute in there somewhere.

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