Alexa Chung, Keira Knightley and Cara Delevingne at The Serpentine Summer Party 2014 Credit: David M. Benett/Getty Images for The Serpentine

Summertime Serpentine style!

Celebrities flocked to London's Hyde Park on Tuesday, July 1, for the annual Serpentine Gallery Summer Party. Not quite as fancy as the Met Gala and definitely not as casual as Coachella, guests including Keira Knightley, Suki Waterhouse and Pharrell Williams, rocked striking dresses and outfits fit for the warm weather.

Knightley wowed in a colorful Chanel gown with an embroidered tier over a tulle skirt. Alexa Chung opted for a ladylike black strapless Erdem gown with a laser-cut hemline, while Cara Delevingne looked statuesque in a black Mulberry gown with a keyhole opening.

An always-dapper Bradley Cooper, in a suit, scruff and shades, accompanied model girlfriend Suki Waterhouse, who wore a dusty pink Burberry Prorsum dress with a deep-V paired with printed Topshop stacked heels. The couple were joined by Pharrell Williams who eschewed the formal dress code in a plaid blazer, white T-shirt, ripped jeans and a felt hat, naturally.

Ladies of London star Caroline Stanbury wore a strapless hot pink Roland Mouret dress, while fellow star Marissa Hermer looked elegant in a ruby-embroidered long-sleeved gown by Alice Temperley.

Princess Beatrice looked angelic in a white Nicholas Oakwell Couture cocktail dress with graduated floral applique. She added a dose of color with lavender sandals and a lime-green clutch.