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Fans of the British royal family are celebrating the birth of the Duke and Duchess of Cambridge's second child, a daughter named Charlotte Elizabeth Diana, born on Saturday. But as Kate Middleton, the wife of Prince William, showed off her new arrival to the world, the focus wasn't just on the newborn - but also on what the duchess was wearing.

Much like in July 2013, following the birth of Prince George, Middleton chose to wear a custom-made outfit by British fashion designer, Jenny Packham. This time around, the dress was white with a yellow floral pattern.

Packham is just one of a string of British designers endorsed by the duchess, who also likes to wear more affordable high street names like Cath Kidston.

Here, CNBC takes a look at which brands have won extra attention and sales because of "the Kate Middleton effect."

- By CNBC's Alexandra Gibbs

Photographer | Collection | Getty Images