SIR Elton John's proudest professional moment came when he performed at late British royal DIANA, Princess Of Wales' funeral - because he had to call on all his skill to get through the somber performance without breaking down.

The rocker performed a special version of his hit CANDLE IN THE WIND at the 1997 service in London, and struggled to maintain his composure in the face of the tragic loss of his close friend.

He recalls, "I had to call on all my professional experience... My voice cracked a little bit on the third verse, but I just hung in there and sang it as a tribute to her. Then I went home with my partner DAVID (FURNISH) and then we cried.

"The most moving thing for me was the coffin in the car going up to her home and people by the side of the road just throwing flowers on it. That's when it hit home."

But there's still one song that Elton can't perform without breaking down - the tune he wrote for assassinated BEATLE John Lennon.

The Brit refused to perform the song, EMPTY GARDEN, during a recent appearance on US chat show INSIDE THE ACTORS STUDIO - because he finds it too upsetting.

He explained, "I don't sing it very often but it means a lot to me because I love the song and I loved John so much.

"Sometimes I play it when I'm in New York, as a tribute because it feels like he was such a New York person... I don't think I can sing that song - it'll be too emotional for me."