Joe Jonas and Ashley Greene’s “London Love Fest”

Joe Jonas (20) and Ashley Greene (23) spent every waking hour together while they were in London — insiders say.

Joe and Ashley were in the British capital for the premiere of the latest Twilight film, Eclipse.

“Ashley brought Joe to the Kings of Leon concert in London, and there was definitely something going on, but it’s not serious,” a source told America’s OK! magazine.

“They went backstage and she was talking to the band a lot, and he was just hanging out.

“I think he wants it to be more than she does right now. She’s a maneater.”

Jonas and Greene also enjoyed a secret date at London restaurant The Ivy.

“They had a very romantic night at The Ivy,” a source said. “They arrived separately and then left out by the back door where there were two vans with blacked-out windows waiting to whisk them away.

“They looked like a lovely couple. They had a few drinks and were clearly enjoying not being hounded like they would have been in Los Angeles.”