George Clooney‘s latest role? Bartender!
The trio, whom Gerber has likened to “one big family,” hammed it up at the Beaumont Hotel in Mayfair on Thursday and were the last to leave the celebration.
“George was hugely jovial. He was just really charismatic and full of energy all night,” an attendee tells PEOPLE. “He didn’t make any speeches but just toured the room talking to and charming the guests. He was just fun, lively, charming and jovial!”
Clooney hopped behind the special tasting bar and crafted cocktails for guests. A source says he encouraged partygoers like Jeremy Piven to opt for just straight tequila with lime if they desired a hangover-free morning.
“There was a tequila old fashioned, a tequila sour, a tequila with Aperol and grapefruit, and tequila on the rocks,” the attendee says. “They were all good and all worked. Tequila twists on the old classics!”
Guests chowed down on steak tartare on brown bread, cucumber and crab bites, and mini fried mac-‘n’-cheeses.
Crawford spent time posing for quick photos with Gerber in the party’s photo booth, and also posted a snapshot of the evening on Instagram.
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Noticeably absent? Clooney’s wife Amal. The human-rights lawyer stayed behind in New York City for work, but will head to London on Monday for a press conference on her case defending former Maldives president Mohamed Nasheed. Her mother, however, was on hand to support her A-list son-in-law.
“George walked into the room with Amal’s mother. They were certainly very friendly and close,” the attendee says. “They spent a lot of time laughing and chatting together. There were lots of introductions with the other guests. He certainly has some kind of mum magnetism! They all love him!”
Crawford held a special signing of her memoir at London’s Waterstones book store in Piccadilly on Friday. The supermodel’s book details her personal life and career.
• Reporting by PHILIP BOUCHER