Nicole Kidman and Keith Urban leave each other love notes

The Oscar-winning actress and the country singer – who have a 20-month-old daughter, Sunday Rose, together – are keen to keep the romance in their marriage alive so write heartfelt messages and leave them in secret places for the other to find.

A source said: "Keith has left notes for Nicole under the pillow and in the shower but the most unique time was when he wrote, 'I Love You', on a skin of orange in the fridge.

"She's not as creative and usually hides them in Keith's pockets, music equipment and even his underwear."

Keith has previously shown his romantic side by writing a song for Nicole.

The 42-year-old musician and his writing partner Rick Nowels penned the heartfelt track 'Thank You' - which includes the lyrics 'I thank God for grace and mercy, and that you became my wife' - and revealed Nicole was thrilled when she first heard it.

Keith said: "Rick's music pulled this story out of me, which became quite a confessional - much more intimate than I might have written had I intended to write about her. It was very instinctual and very much from the heart. We did a quick recording of it, and I took it home and played it for her that night. I think she was very touched."