Other stars whose personal details he obtained include Lloyd Cole, Lionel Ritchie, the dancer Michael Flatley and Barry Humphries.
Among items seen by The Independent are tour arrangements for Sir Elton, details of a private performance he gave for the Sultan of Brunei, the home telephone numbers and worldwide addresses for a host of stars and even an internal memo to staff warning them to be careful of how they dispose of their rubbish. Some documents bore the words "To be shredded".
Benjamin Pell, 34, who is now being sued by Sir Elton and the agent, John Reid Enterprises, says he amassed 75 bags of papers, including bank statements, confidential legal correspondence and tour arrangements before being stopped by a High Court injunction.
For six months after the death of Diana, Princess of Wales, Mr Pell kept an electronic and physical vigil on the London offices of Mr Reid in the hope of discovering secrets about her friendship with Elton John, whose song "Candle In The Wind" was re-dedicated to her.
"I couldn't believe my eyes when I saw how easy it was to get hold of this stuff," Mr Pell, who also works as a freelance music journalist, told The Independent. "I went through their rubbish and I got some very clever computer nerds to hack into the system for me. Getting into the computer system was even easier than getting into the rubbish.
"I am a fan of Elton's and I wondered whether I could find anything out after Diana's death. I certainly don't usually go through people's rubbish or hack into their computers."
Through his dual snooping, Mr Pell found copies of Elton John's bank statements and letters from his accountants, Price Waterhouse, expressing concern over his rates of expenditure on luxury items. These details were published in the Mirror newspaper, resulting in writs being issued against Mr Pell, the publicist Max Clifford and the Mirror.
He also found copies of letters from Sir Elton and Richard Branson arguing over the inclusion of "Candle In the Wind" on a charity album. He insists that the Price Waterhouse letters and the Branson exchanges were found in rubbish outside the agent's offices.
Mr Pell is now limited in what he can say about the affair. Lawyers for Mr Reid succeeded in having a strict Anton Piller order issued against him, allowing them to freeze his assets and search at his address. They did not manage to recover any of the documents, which The Independent understands are still in existence, possibly abroad.
Mr Reid is in Australia on business. Nicola Turnbull, his director of business affairs, said the company was unable to comment because of the pending legal actions. It is understood, however, that the company will deny that confidential information was thrown out as rubbish.