Paying sartorial homage to their late mother-in-law, though neither woman ever met her, guarantees a barrage of headlines both in the UK and internationally, with fans and critics alike also poring over the comparative looks on social media.
It's unsurprising both the current Princess of Wales and Duchess of Sussex mirror or echo aspects of Diana’s style – you’d be hard pressed to find a trend entirely untouched by Diana’s influence over the last couple of decades.
However, Meghan and Kate, but particularly the current Princess of Wales, take it a step further with incredibly explicit fashion tributes.
So, why are the two women so keen to emulate Diana, rather than carve out a more distinctive style of their own?
“I think now the comparisons are most notable in Kate but that's probably because she makes many more public appearances than Meghan," says Bethan Holt, author of The Duchess of Cambridge: A Decade of Royal Style and The Queen: 70 Years of Majestic Style.
"Plus, the clothes Kate's wearing for her engagements are dressed-up and smart and there's over a decade of similarly polished Diana looks to compare these with so comparisons are bound to happen.
"I'm sure it would be something both women would discuss with their husbands when it's intentional but it's a fitting way to pay tribute to Diana, given that fashion was something she was so well known for. It's a nice way to keep her memory alive in a very non-controversial way."
While Holt feels some of the comparisons are coincidental, another expert – fashion psychologist Carolyn Mair – felt they were likely to be more purposeful.
"Our clothes don’t just fall on us so the notion of dressing like Diana subconsciously is very unlikely," Mair tells Yahoo UK. "I would assume a great deal of thought goes into both the royals' looks and so what they wear is a conscious decision."
Holt says some of Kate and Meghan's most memorable looks that spurred comparisons to Diana crossed decades and demonstrated the expansiveness of the former Princess of Wales' style.
“I always think of the Prada dress which Kate wore to mark the 20th anniversary of Diana's death. With its delicate floral print and pussy bow neckline, it reminded us of Diana's early '80s style - a time when she was so young and innocent, and before all the drama which later unfolded had truly begun.
“More recently at Trooping the Colour, you could really feel a Diana influence in the bold emerald colour of Kate's Andrew Gn outfit and her wide-brimmed hat was just like something Diana would have worn in the mid '80s," says the royal author.
"This felt like tribute to Diana as a power dresser, at the height of her 'Dynasty Di' era."
When it comes to Meghan, we've seen more references to '90s Diana, Holt explains.
"The jeans and white shirt she wore for a charity visit in LA were very similar to the looks Diana wore for her more relaxed engagements after her divorce," she says.
Through their marriages, both Kate and Meghan have access to the late Diana’s enviable jewellery collection and pay tribute to her this way.
Meghan regularly opts for Diana’s Cartier tank watch while Kate’s sapphire engagement ring is the very same one her mother-in-law wore.
Mair notes: "Imitation is the sincerest form of flattery, or so the saying goes. Diana was admired and loved by millions. She was probably one of the most loved royals in history so emulating her look would be a way to demonstrate their admiration of her."
While it certainly demonstrates that Meghan and Kate think highly of their mother-in-law’s fashion impact, it also raises the possibility that they are keener to align themselves with someone so universally beloved than to take over her role of trendsetter and innovator.
"Looking back now, we certainly see Diana as someone who really used fashion to her advantage and had a lot of fun with it," Holt says. "I think she really grew into her role as a fashion influencer in the 90s when she was much more confident and knew how to wield her fashion power. What Meghan and Kate do (Kate especially) is take existing trends and make them much bigger and more relevant.
"Once they've worn a trend, the world takes notice."