The annual Serpentine Gallery party to open its summer pavilion (always a temporary structure by a guest architect) had everything this year—sponsorship by Swarovski, extra-glittery guests, chandeliers, dancing in the park—except one tiny detail. Somehow, the pavilion itself had gone AWOL. In the run-up to London's biggest summer bash, it became clear that Olafur Eliasson's structure wasn't going to be ready in time for its inauguration. With social disaster looming, Zaha Hadid stepped in at the eleventh hour and built four glowing mushroom parasols to shelter the dance floor. "They're steel structures covered in fabric. Did it in four weeks," she said. To say that Nadja Swarovski was visibly relieved is an understatement. "Zaha rocks! She saved the day. What an example of creative problem solving," she said.

And happily, Rod Stewart, Pierce Brosnan, Tracey Emin, and Geri Halliwell, among other guests drawn from the farthest-flung poles of London/L.A./Euro society, seemed to be having too good a time to notice the absence of Eliasson's pavilion. Practically all of the city's young designer community showed up— Christopher and Tammy Kane, Jonathan Saunders, Richard Nicoll, and Hussein Chalayan included. Giles Deacon chatted with Thandie Newton about his flash visit to L.A. with his pre-collection; Sophia Kokosalaki and Liz Goldwyn arrived, both in Kokosalaki's bright draped dresses and the latter accessorized in Van Cleef & Arpels; and Stefano Pilati, in town to film a 24-hour shoot for his new Edition 24 collection, which will be live-streamed on www.showstudio.com this weekend, came with Camilla Nickerson, who was in a short YSL tux dress. Also tuxed was Phoebe Philo, just four weeks after giving birth to her son, Marlowe, who, she said, was named after the dark Renaissance playwright. And Cameron Silver of Decades dropped by with Clare Waight Keller of Pringle—he was sporting a bespoke suit and she was in a vintage Dior coat snapped up that day at Alfies Antique Market.

This being London (and a garden party with the threat of rain a constant), there was no discernible dress code, except, of course, for the Swarovski-tribute glitter—lots of it supplied by the crystal accessories that Kane, Saunders, and co. have designed for the house. Ironically, it was all lent out before the party-giver could grab a piece for herself. She had to resort to diamonds by London rock-meister Stephen Webster.

— Sarah Mower