Kate Middleton Looks Slim in Designer Dress at the Portrait Gala: Pictures

Duchess of Cambridge Kate Middleton looked elegant in a Jenny Packham gown at the Portrait Gala on Feb. 11 in London Credit: Splash News Online

Mommy's night out!

Fresh from her family vacation with Prince George in Mustique, Kate Middleton swapped her favorite navy jeans for a navy dress for The Portrait Gala 2014 at the National Portrait Gallery in London on Feb. 11.

The elegant blue silk tulle Jenny Packham gown features a black velvet belt to highlight her tiny waist and gathered material on the sweetheart-necklined bodice. Middleton debuted the dress in October 2013 at the 100 Women in Hedge Funds Benefit Gala.

The Duchess, 32, complemented the simple-yet-stunning gown with bling fit for the queen -- literally. The "Nizam of Hyderabad" necklace was a wedding gift to Queen Elizabeth II and loaned to Middleton for the event. The 1930s Cartier necklace consists of 38 diamonds on a chain and a center pendant with 13 emerald-cut diamonds.

Middleton wore her signature loose-waves hairstyle and kept her makeup simple and sophisticated with a subtle smoky eye and pink lips.

While Prince William didn't attend the Portrait Gala, the event marks Middleton's first royal outing of 2014.

During the dinner, Middleton highlighted the gallery's accomplishments. "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," Middleton, patron of the gallery, said. "But, it is more than simply a world renowned visitor's attraction. The gallery's outreach and research programs make it one of the leading centers for the important study into portraiture. I could not be more proud to be its patron."