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By Laura T. Coffey

At her first official engagement of 2014, Duchess Kate dazzled onlookers Tuesday night with a longer hairstyle, a stunning Jenny Packham gown and something else: Serious royal bling, borrowed from her granny-in-law.

Queen Elizabeth II loaned Kate the diamond necklace she received as a wedding gift for her marriage to the Duke of Edinburgh in November 1947.

Known as the Nizam of Hyderabad, the necklace was created by Cartier in the 1930s. Queen Elizabeth has worn it for a number of formal portraits.

On Tuesday, Duchess Kate sported the necklace to a benefit gala for the National Portrait Gallery in London. She spoke briefly to guests about the importance of the event.

Catherine, Duchess of Cambridge, wore Queen Elizabeth's diamond necklace to a benefit gala for the National Portrait Gallery in London. Today

“I just wanted to say how delighted I am to be here this evening to celebrate the fantastic work of the National Portrait Gallery,” Duchess Kate said. “The Gallery’s achievements are exceptional. They hold the most extensive collection of portraits in the world, and their unique and brilliant exhibitions never fail to inspire us all. ...

“I simply could not be more proud to be its patron.”

Kate’s husband, Prince William, was not present at the gala, but several celebrities were, including actress Elizabeth Hurley, musician Bryan Adams, actor Alan Rickman and artist Grayson Perry.

Catherine, Duchess of Cambridge, wears everything from fancy hats to casual tank tops. See how Prince William's wife can easily go from a high society affair to shopping on the streets of London.

Known for recycling dresses, the Duchess demonstrated her thriftiness by wearing her navy blue, floor-length Jenny Packham gown for the second time. She first wore the dress last October to a 100 Women in Hedge Funds gala.

Last December, Duchess Kate made headlines for wearing Queen Elizabeth's diamond tiara for the first time since her wedding.