Jon Hamm "couldn't leave" Kate Beckinsale at a screening of his new movie.

Jon Hamm

Jon Hamm

The former 'Mad Men' star was reportedly flirting with the 43-year-old actress at director J.J. Abrams' Los Angeles event for 'Baby Driver' and despite there being a number of other guests to mingle with, including Sacha Baron Cohen, Ava DuVernay, Jack Black and Jon Favreau, the 46-year-old star only wanted to talk to Kate.

An onlooker told the New York Post newspaper's Page Six column: "They were flirting and he kept going back to her all night. It was like he couldn't leave her.

"She had a friend with her, but they were kind of ignoring her and just talking to each other. He was leaning in to talk . . . [Kate] was laughing and giggling."

Jon has been single since splitting from his long-term partner Jennifer Westfeldt over 18 months ago, while Kate - who has 18-year-old daughter Lily with ex-partner Michael Sheen - split from her husband Len Wiseman in November 2015.

Kate is known for the close friendship she has retained with Michael, and recently admitted he will always be "family" to her.

Asked what the secret is to their longstanding friendship, she said: "Well one, pick well. And two, I think we both really felt like, we really agreed on what would be the right thing for Lily. And I think, you know, not hating each other and fighting and all that would be awful for her.

"I think we've also got a really similar sense of humour, and I do find that humour can save an awful lot of things and help a lot of things. I just really like him. He's family. I've known him since I was 21, so he's proper family now."

And Kate regularly spends time with the 'Masters of Sex' star and his current partner Sarah Silverman and the group tend to spend Christmas and Thanksgiving together.

She added to Entertainment Tonight: "Well, we had Thanksgiving at his girlfriend's house and they're having Christmas at our house. We like hanging out with each other, so it's not like, 'Oh, who gets Lily?' or whatever. It's like, 'Whose house are we going to be at?'"

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