Call it the "royal flash".

The Duchess of Cambridge Catherine Middleton did an 'Angelina Jolie' at the Thirty Club Dinner in the plushy Claridge's Hotel in London. The wife of Prince William arrived at the said event wearing a high-slit dress revealing a small view of her legs.

The Thirty Club is an elite group that meets once a month at the said hotel to socialize and discuss advertisement issues.

The 30-year-old royal fashionista wowed everyone at the private dinner. She was wearing a cream gown done by Roland Mouret, and swanky stilettos and earrings by Jimmy Choo.

Middleton was accompanied by none other her husband Prince William. The couple looked regal and stunning even if they opted for a low-key celebration of their first wedding anniversary.

Prince William, who was a speaker at the gathering, was said to have accepted the exclusive group's invitation because he is due to celebrate his 30th birthday on June 21.

"The Duke has been invited for around nine years now and thought that it was right to accept the invitation this year because of the Queen's Diamond Jubilee. It also seemed rather apt as it his 30th birthday next month," a rep for the royal couple said.

"Other senior members of the Royal Family also suggested that it was an interesting event to attend." "He thought it's right to accept the invitation this year as he has this personal landmark coming up and it is such a landmark year for the royal family in general," a senior royal aide added.

Aside from the said dinner event, the royal couple will likewise serve as dignitaries to Our Greatest Team Rises, a dinner to honor the Paralympics Great Britain and Team Great Britain for the upcoming Olympics. The two will join other dignitaries in extending their support for the British National teams in this year's Olympics to be held in London.

Kate Middleton and Prince William tied the knot on April 29, 2011. The royal wedding was watched by millions of people around the world.