Elliot Page and Olivia Thirlby starred in Juno. Off-camera they were "having sex all the time".

In his new memoir Pageboy, Elliot Page writes about his relationship with Juno co-star Olivia Thirlby – detailing how they became more than friends on the set of the 2007 film.

"I was taken aback the moment I saw Olivia Thirlby," Page, 36, reportedly wrote in the book, which came out this week.

Although they were both 20 at the time, he said Olivia seemed "so much older, capable, and centred" than him – "sexually open, far removed from where I was at the time."

"But the chemistry was palpable, it pulled me in," Page wrote.

The actor recalled the moment their friendship turned into something more.

"We stood in her hotel room. Billie Holiday played. She was about to start making lunch, when she looked directly at me and said point-blank, 'I’m really attracted to you.' 'Uh, I’m really attracted to you, too,'" Page wrote in the memoir. 

"At that we started sucking face. It was on."

"We started having sex all the time: her hotel room, in our trailers at work, once in a tiny, private room in a restaurant," he added.

Image: Searchlight Pictures.

The actor came out as gay in 2014 and as transgender in December 2020. 

The same year he came out as gay, the now 36-year-old was in another relationship with an actor – this time, Kate Mara.

The two of them were filming X-Men: Days of Future Past; and Mara was in a relationship with someone else.

"The first person I fell for after my heart was broken was Kate Mara," Page wrote in the book. 

"She had a boyfriend at the time, the lovely and talented Max Minghella."

"This was right after I’d come out as gay and it was a time of exploration and also heartbreak," he said.

"I think my relationship, or whatever you want to call it, with Kate very much encapsulates a certain dynamic that I consistently found myself in, which was falling for people that – I think a lot of us do this – aren’t fully available.

"And the sort of safety in that and the highs and the lows and the serotonin bump and then it goes away. And I think that is definitely a pattern in my life."

While Page and Mara eventually ended up going their separate ways, the two are still really close. Mara even got to read the book before it hits the shelves. 

She’s even going to join Page for an event to promote Pageboy in Los Angeles this month. 

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A post shared by Kate Mara (@katemara)

"I think the love and care that we have for each other is its very own special thing," Page said. 

"Separate from the intimacy that I write about."

While Page discusses other relationships in the book, he keeps the rest of the names anonymous - including a closeted co-star he dated for two years.

"Feeling hidden was far too painful. That was impossible and not a sustainable relationship at all. And it taught me that I was not gonna do that again," he said of that time.

Feature image: Instagram/@elliotpage/Searchlight Pictures.