The fuchsia dress the Duchess of Cambridge wore for the royal family's first official portrait with baby Prince George has sold out in stores all over Britain.
Prince William and his wife released the first official photographs of their baby boy on Monday - and in a break with tradition they were taken by her father Michael Middleton.
Just 24 hours after the photo was released worldwide, royal fans flocked to buy the STG46 ($A80) outfit.
The short-sleeve Jolene dress from Seraphine Maternity has appealed to many mothers because of its flattering silhouette and vibrant colour.
Seraphine Maternity's online site states the item is currently unavailable: "Due to high popularity of this style, please be advised that orders will be dispatched week commencing 16th of September."
It's not the first time a label has been hit by the "Kate effect".In 2010, when Kate and William announced their engagement, the dark blue Issa dress she wore also sold out within days.