Mischa Barton was on hand in London to unveil what is said to be "the most expensive cell phone case in the world."

UK-brand Uunique claims that its London Lotus iPhone 5 case, which is emblazoned with 18-carat rose gold, pink and white diamonds, is the priciest on the market at 302,985 dollars, the New York Daily news reported.

Barton, best known as the star of the 'The OC,' presented the blingy accessory while showing off her own, less expensive designs for the company.

" Uunique approached me and I thought it would be a really interesting thing to design something that was both functional and fashionable," Barton told the tech site T3.

Barton, who dressed in a gem-studded maxi dress with sparking headband for event, said she wanted to take a fashionable approach to designing cases for the iPad and iPhone.

"We wanted to incorporate different types of embroidery and embossing and different fabrics. I see a lot of use for different kinds of fake metals and Perspex, fake wood, cork and plastics and to just see what you can do," she said.

"Unique by Mischa" cases start at 40 dollars and go up to 960 dollars for a Swarovsky crystal encrusted model.