Mario Testino / Getty Images

Kate Middleton showed people's princess flair when she posed with fiance Prince William wearing apparel from some of the United Kingdom's mid-priced retailers - not exclusive designers - for her official engagement photos.

While the United Kingdom's future king and queen got the supermodel treatment by posing for famed Peruvian fashion photographer Mario Testino on Nov. 25, their first joint portraits taken in the formal Council of Chamber at St. James Palace in London have a relaxed feel.

Testino described the royal couple as "brimming with happiness" during their session. "I have never felt so much joy as when I see them together," the photographer said in a statement.

In a touching close-up Middleton is being embraced by Prince William, her Princess Diana heirloom 18-carat diamond and sapphire engagement ring resting on her groom-to-be's shoulder.

Middleton is wearing a flattering off-the-rack cream scallop-edged blouse with floral applique that The Telegraph reports is from the upcoming spring collection of UK retailer Whistles. At a retail price of about $142 we predict it will become a royal sell-out just like Middleton's much-copied Issa engagement announcement dress.

The prince is wearing a beige/brown cashmere sweater by the Italian house of Brunello Cuccinelli, which the newspaper reports was lent to him by Testino -- probably to give the portraits a more casual feel.

In a more formal portrait, the couple stand side-by-side in what appears to be a posed embraced with the staid furnishings of the palace in the backdrop. For this portrait the prince is wearing a navy suit and tie by royal shirtmakers Turnbull and Asser. Middleton's dress is by British retailer Reiss. The knee-length "Nanette" dress in ivory has a belted waist, petal skirt and feminine draped collar and is valued at approximately $268.

On Monday, Reiss announded it would re-release "a version of the dress style Kate chose," to be "available beginning in January 2011, as part of the Reiss Spring/Summer 2011 collection."

Royal copy-cats on this side of the pond can find Reiss stores in American cities including New York, Boston, Los Angeles, Boca Raton, Fla., and Washington, D.C. And the Daily Mail is reporting there are already bidding wars on used versions of the dress.

Meanwhile, read what piece of souvenir apparel has been banned from bearing the signature portraits by the royal household.

And read about the sheer dress Middleton was wearing when she met her prince charming that is now a valuable royal artifact.

Want more? Click here to check out Kate's best style moments.