Hundreds of millions of TV viewers watched as Kate's mum Carole showed up in a blue Kiely dress to St, Mary’s maternity hospital in London on Tuesday July 23, turning the outfit into an instant success.
Carole wore arrived in a $503 (£330) pebble hue tea dress from Kiely's collection. The fashion designer, who is originally from Dublin, told the Irish Independent it was a “pleasant surprise”.
"She must have had the dress and decided to wear it," she explained. "I did think she looked great. She's very elegant and slim, and has good style. She was radiant on that particular day."
Kiely also spoke about a boost in sales as a result of the 'Kate Middleton effect', when clothes sell out nearly immediately after the Duchess of Cambridge wears them.
“It does create great awareness and that's always important.”
"We don't 'dress' people as such,” Kiely explained.
“But we have certain people who like the brand so they go for it. Keira Knightley is one. Alexa Chung is another, which is great because she's such an ambassador of fashion. It's lovely to see anybody wearing the designs and enjoying it."
The designer, who is based in London, told the newspaper she tries to get back to Ireland a few times a year.
"I try and get home as often as I can, maybe twice or three times a year. I have young family here.
"Seeing family is the most important thing, but I absolutely love to go for a walk on the beach. I couldn't do it this time because I have a broken foot, but where I grew up was a two minute walk from the beach. That's something I don't have in London. I grew up in Shankill, and the walk from Shankill to Killiney - there's nothing like it."