Nicole Kidman has revealed she bought the original handwritten lyrics sheet for Sir Elton John's 'Your Song'

The 'Babygirl' star - who performed a duet of the tune with her country music star spouse Keith Urban, 57, in 2019 - treasures it so much, she wasn't willing to share where she keeps it.

Talking about signing autographs on 'The Late Show With Stephen Colbert' this week, Nicole said: "Well, I've asked people to sign a copy of a book. Philip Roth and Elton John."

She continued: "That was because we bought lyrics of 'Your Song'."

The host then asked her: "Where do you keep those?"

Putting her finger to her lips, she said: "Shh."

The couple had posted a clip on Instagram of Keith on the keys as they belted out the song.

Meanwhile, Keith recently hailed Nicole's decision to do the erotic thriller 'Babygirl' "incredibly brave".

The actress plays a high-ranking CEO in the X-rated film, which she recently branded her most "exposing" project to date, and her other half told 'The Sunday Project': "She's incredibly brave with her choices."

Nicole recently told Vanity Fair: "I've made some films that are pretty exposing, but not like this."

The 'Bombshell' star felt particularly anxious about her sex scenes.

The Hollywood star explained: "It's like, golly, I'm doing this, and it's actually now going to be seen by the world. That's a very weird feeling."

The 'Big Little Lies' star hopes the flick proves to be a "liberating story" for women.

She said at the Venice Film Festival: "This is one woman's story and this is, I hope, a very liberating story.

"It's told by a woman, through her gaze - Halina [Reijn] wrote it and she directed it - and that's to me what made it so unique because suddenly I was going to be in the hands of a woman with this material. It was very dear to our shared instincts and very freeing."