LONDON — The stars stayed cool in the summer heat with cold pints of beer and ice on their wrists at Jessica McCormack’s Summer Solstice Party this week at Mount Street Gardens in Mayfair.

Diamonds weren’t the only things shining on the night. Cohosts Zoë Kravitz and Carey Mulligan cohosted “McCormack’s Tavern,” a British pub-inspired garden party with guests including Drew Barrymore, Jodie Comer, Caitriona Balfe, Alexa Chung, Poppy Delevingne and Sheila Atim. 

Kravitz, a brand ambassador who describes McCormack’s rocks as “diamonds with attitude,” wore a thick, white gold armband emblazoned with “JMc,” and embellished with a seven-carat diamond charm. She paired the sparkles with a sleek one-shouldered gray slipdress. 

For Kravitz, it’s a white gold kind of summer. “It’s fresh, it’s punk and it’s kind of masculine, which I like,” she said of the jewel. “I’m a little nostalgic for the ’90s, and I think that also reminds me of my teenage years.”

McCormack’s brand is all about playfulness. Her latest collection features pearl necklaces dangling with starfish and gold smiley faces studded with diamonds. “I want to create something that’s a forever piece, no matter the season or the collection,” McCormack said. “I see people here today, and they’re wearing things from 15 years ago.”

Guests were celebrating McCormack’s redesigned, two-story flagship — the Townhouse, on Carlos Place — just a few steps from Mount Street Gardens. There, chic diamond necklaces lay in glass boxes on navy blue velvet, and bracelets, earrings and rings were on show in custom antique jewelry boxes made from an assortment of 1950s tins. 

Back at the outdoor “pub,” McCormack’s guests did not make like the Druids and light bonfires to celebrate the solstice. Instead, they played a variety of nostalgic carnival games, like Hook a Duck, Beat-the-Buzzer and High Striker, all around the garden.

McCormack’s hope was to bring everyone together under one common denominator: beer. Guests stayed cool under the large trees with custom taps of “McCormack’s Lager,” gin and tonics, and Lost Explorer tequila margaritas. 

Each guest was given a numbered token, and at the end of the night, McCormack, Kravitz and Mulligan each called out three winners to pick up their very own diamonds.