The royal stepped off the plane on Prince Edward Island over the weekend wearing a chic cream shift dress from Joseph - and of course, the second it was identified, it started flying off the shelves, selling out in a matter of hours.
And even better for Kate style copycats? The Vanessa sleeveless crepe dress, originally £275, had just hit the summer sale - meaning it was retailing for a far more affordable £165.
It's hardly the first time the Duchess has prompted a high street buy to sell out - remember that Reiss Shola dress which crashed their website?
Click on our gallery below to see what William and Kate have been up to during their royal tour of Canada: