Sir Elton John's friends once spiked his dinner with cocaine to make him play the piano all-night.

In a new documentary focusing on how he became a superstar in America, the singer-and-pianist reveals his pals put the class A drug in his food to improve his performance.

Elton, 63, said: ' left at 7.30 in the morning and I thought, 'I've never stayed up until 7.30 before but I feel really good!' Years later I learned they had put cocaine in my food."

Rocker Danny Hutton, who played in US rock band Three Dog Night, admitted he was behind the spiking, saying: "I might have forgot to tell him. Well it certainly didn't hurt him. He went on to be quite successful."

The documentary, titled 'Madman Across The Water: The Making Of Elton', charts Elton's rise from an unknown British musician to a huge star in the late 60s and early 70s.

Talking about how he found himself hanging out with the biggest stars of the day ' including Bob Dylan and Beach Boys mastermind Brian Wilson - Elton said: 'n two months I met some of the greats of the music world, it was joyous.'

Elton has also confirmed he has recorded a duet with Lady Gaga, titled 'Hello, Hello,' which will appear on the soundtrack of Disney film 'Gnomeo and Juliet', which is being produced by Elton's husband David Furnish. Gaga and Elton previously collaborated together for a performance at the Grammy Awards in January.

Elton is to play a show in London next Thursday (28.10.10) as part of the BBC Electric Proms concerts.