The memorable outfit she wore to the 1987 film festival - a light blue tulle dress - came complete with a scarf and paired with blue shoes. It is thought to have been inspired by Hollywood legend Grace Kelly, who became the Princess of Monaco in 1956.

       She wed Prince of Monaco Rainier III a year after starring in Alfred Hitchcock's To Catch A Thief, led by Cary Grant.

       In the movie, Kelly wore a classical Greece-style dress in blue hues.

       Princess Diana purportedly worked closely with fashion designer Catherine Walker to craft a gown similar.

       Tatler’s Rebecca Cope described the meaning behind Diana’s inspiration.

       She wrote: “It was an homage pregnant with meaning, with the actress of course going on to become royalty herself when she married Prince Rainier III of Monaco.

       “Diana and Grace had met in real life in 1981, with the Monégasque royal reportedly giving the newlywed advice on how to handle the pressures of the limelight.

       “It was on this occasion that Diana - then still Lady Diana Spencer - made a fashion faux pas, wearing a low-cut, black gown by the Emanuels, which was not only considered too risqué but also inappropriate, as black is reserved for funerals only.

       “A year later, in 1982, Princess Grace would die in a car accident in Monaco, a foreshadowing of Diana's own death 15 years later.”

       Now, over two decades after Diana’s tragic death, Kate Middleton pays tribute to her late mother-in-law through her own fashion choices.

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