The work of a New Zealand fashion designer is proving popular with the Duchess of Cambridge who has again chosen an Emilia Wickstead creation for a public royal engagement.

Thirty-year-old Catherine wore a STG1200 pale-yellow coat dress in Edinburgh on Thursday when she attended a ceremony where her husband, Prince William, was installed as a Knight of the Thistle, Scotland's highest honour.

The outfit, complemented by black suede heels and a subtle latte-coloured sisal beret, surprised some British commentators who described yellow - a colour worn in public only once before by Catherine - as an unusual choice.

The beaming Duchess carried a folded tartan scarf, a nod to her Scottish title: Countess of Strathearn.

At a May state lunch, British media described Catherine as "pretty in pink" when she wore a pink coat dress designed by New Zealand-born Wickstead, who is now based in the UK.