Aniston dating Gerard Butler?

Is Jennifer Aniston swapping men with Cameron Diaz again?

Jennifer Aniston, it seems, likes swapping boyfriends with another hot hollywood singleton: Cameron Diaz. This time? It's Gerard Butler, according to US reports.

After splitting with her boyfriend of four months, John Mayer - who previously dated Diaz after she split from Justin Timberlake - insiders say Jen is back in the dating game, and has set her sights on 300 hunk Gerard, who also recently enjoyed a few dates with Cameron.

Jen and Gerard were seen flirting at a bar during the Toronto Film Festival, where Aniston was promoting her new movie, Management, and Butler was there for the world premiere of his new Guy Ritchie film, RocknRolla.

And an onlooker spotted the pair enjoying each other's company at the Park Hyatt Roof Lounge after the screening of Aniston's movie. The source told InTouch Weekly: 'They immediately made eye contact. They had instant chemistry.'

Another partygoer said: 'It didn’t take Gerard and Jen long to gravitate to one another. When they came together, it was all hugs and smiles.

'She was playing with her hair and acting coy.

'At one point, Gerard had his hand on her thigh and was whispering in her ear.'

Then, according to the Daily Mail, after spending most of the evening together, the pair left at the same time, with Butler rubbing Jen's shoulders and kissing her on the head.

Jen's possible new love interest comes just weeks after splitting from musician John Mayer, who spoke about his split from Jen in a video interview, saying: 'Have me as a man who ended a relationship stand here and write some truth.

'Have me stand up for somebody and write that Jennifer Aniston is the smartest, most sophisticated person I think I've ever met.

'She's one of the most lovely people I've ever met in my life and I'm going through something that's a very personal thing and you have to give that up...

'There's no lying, there's no cheating. There's no nothing. People are different, they have different chemistry, they have different lives.

'I ended a relationship because there is no lying. I ended a relationship to be alone because I don't want to waste somebody's time if something's not right. I don't waste people's time.'

How noble. Looks like Jen's moving onwards and upwards with buff Butler, anyway.

Meanwhile, Cameron Diaz is happily enjoying a new relationship with Brit model, Paul Sculfor who, last year, funnily enough, enjoyed a series of dates with, yes, you guessed it, Jennifer Aniston.

It's a small world...

JENNIFER ANISTON PICS.

CAMERON DIAZ PICS.