Like a true Princess!

The Duke and Duchess of Cambridge stepped out Tuesday night to attend the Diplomatic Reception at Buckingham Palace, and Kate was dressed as regal as ever. The Duchess was seen wearing a tiara for the first time since her wedding day in April 2011.

Kensington Palace has confirmed that the sparkling diamond tiara, once belonging to the Queen Mother and Princess Margaret, was loaned to Kate for the evening by the Queen. Kate wore her hair half up to put the tiara on display, maintaining the sparkle with another borrowed piece: the Queen's diamond earrings. Her dress, which has a high lace neckline, was a bespoke evening gown by Alexander McQueen. (Okay, major Royal Wedding flashbacks!)

The Diplomatic Reception, held every year by the Queen of England, is one of the largest events held at the Palace with over 1,500 guests. We were so excited to hear that Kate and Wills were going to attend the lavish event, because Kate is still technically on maternity leave, and the pair had said they wouldn't attend any white tie events until at least 2014. White tie is more formal than black tie -- requires men to wear white ties, women to wear long gowns and a tiara (if they have one). It's a clear movement for the couple into solidifying their place in the royal family!

We were hoping to get a glimpse of Kate's gown, but for now, we'll settle for the diamonds. No doubt our favorite Duchess stole the show.

Photo Credit: Splash News