Sir Paul, 59, and Mills, 33, announced their engagement in July, three and a half years after his wife of nearly 30 years died of cancer.

Linda McCartney died in 1998

He met his fiance�, a model and anti-landmine campaigner, two years ago at an awards ceremony.

When their romance was made public, Sir Paul disclosed that his feelings for Mills had inspired his music.

He said: "It's really nice if you have a romance for song-writing."

In the interview, Sir Paul also talked about his difficult relationship with the late John Lennon's wife Yoko Ono.

Sir Paul said he thought there was "still time" for them to improve their relationship.

Sir Paul's daughter Stella is f�ted by the fashion world

They recently fell out over whose name should go first - his or Lennon's - on the writing credits for Yesterday on The Beatles Anthology.

He said he had written the song and wanted to have his name before Lennon's, and dismissed the idea that he felt threatened by Lennon's legacy since his murder in 1980.

"People now think it's a major bone of contention with me, like I'm worried about being overshadowed by John," he said.

"I'm not. I love him dearly. I think he would have done it but it's one of those things that happen in life and I'm OK with it now.

"But if you're reading this, Yoko, there's still time."