George Michael Records Royal Wedding Song

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"The idea came to me last week... that I should express my happiness at this marriage," he explains on "Piers Morgan Tonight."

George Michael was good friends with Princess Diana -- and now he's recorded a royal wedding song for her son, Prince William, and his fiancee, Kate Middleton.

Michael premiered his cover of Stevie Wonder's "You and I" on CNN's Piers Morgan Tonight Friday.

Beginning at 9 p.m. ET Friday, the song was available for free on his Web site,, with any donations going to

Michael called recording the song the "best two days of work of my life."

"The idea came to me last week... that I should perhaps kinda express my happiness at this marriage, in a way, publicly," he told Morgan.

"It was an April day that happened to be like summer here in London and I was Twittering and kinda got carried away and decided I was gonna make them [William and Kate] a new track... by Friday, so I've had a very busy week," he continued.

"When I was a child I dreamt of singing this song in my imagination... I used to dream of singing it in the school assembly hall, but I guess this is a slightly bigger deal than that," he added of the song.

"It's not just a gift for them, it's a gift that they'll be able to turn into many, many donations for the, which is where they've asked people to give money rather than send presents," he went on.

"I would really like for any of my fans or anybody who really enjoys this track, if they're gonna download it for free... I would love them to go to Kate and William's charity site and make a donation if they're genuinely happy for these two people, which I think a lot of people are."

Wonder waived the fee rights to his 1972 song until "way after the wedding," Michael said, so more money could be donated to charity.