Jamie Foxx, Sienna Miller and Sean Combs made a cozy threesome at the Golden Globes after-party hosted by InStyle and Warner Bros.


“Diddy and Jamie Foxx were sitting together,” says our spy, “but when Diddy saw Sienna, he went over to meet her. He got her cell phone number and invited her to sit with them.”


According to our source, the dapper rapper made plans to meet Miller at the CAA after-party at the Sunset Tower Hotel, but when he arrived, security wouldn’t let him in. When he demanded “Do you know who I am?” a doorwoman for the party responded, “I know exactly who you are, and you’re not invited.” Diddy must be with a competing agency.


Meanwhile, Hilary Swank’s limo was stopped by award-show security when it didn’t have the proper parking pass. The “Freedom Writers” star hopped out with boyfriend/agent John Campisi and hitched a ride to the ceremony in another car — but not before turning on the unsavvy security and “flipping them off.” Says our spywitness, “I’m calling it her ‘Million Dollar Finger.’ ”


Drew Barrymore looks like she’s skewing older since her rumored split from Strokes rocker Fabrizio Moretti. The actress was locking lips with Bruce Willis at the party Prince threw at the Beverly Wilshire. “They were making out in front of everybody,” says a spy.


And busted-up couple Justin Timberlake and Cameron Diaz had a surprise reunion at the InStyle party.


“When he first came in, Justin steered clear of her,” says a spywitness. “But he made a beeline toward her when he saw her sitting on a couch with [her ‘Gangs of New York’ co-star] Leo DiCaprio.


“Justin smiled and raised his glass to Cameron and she did the same. Then he slid in next to her.


“They spent about 15 minutes talking, but didn’t want anybody taking their picture.”