The Princess and the butler: the final chapter

The long-running battle between Paul Burrell and the Royal Family should finally come to a conclusion next week when Princess Diana's former butler publishes a new chapter for his best-selling autobiography, A Royal Duty.

Mr Burrell has added 14,000 new words to his story, provoking speculation that he is finally about to disclose the "big secret" that Diana said she was keeping just before her death.

"This is his last shot," Clarence House was reported as saying yesterday. "Then we can move on."

Diana's teasing of reporters in 1997 led to suggestions that the Princess was about to marry Dodi Fayed or have a baby by him. It later fuelled rumours that she had been murdered.

Mr Burrell finished the first version of his book with the provocative words: "What's the secret? That's between the butler and the Princess."

Mr Burrell's publisher, Penguin, is working hard to avoid the contents of the new chapter being revealed before its publication on 1 June. "It's a closely guarded secret," said a spokeswoman. "I've no idea what's in it. There is a new chapter, that's all I will say. There is new material in the new chapter."

Mr Burrell's agent, Ali Gunn, told Publishing News: "I think the new material is certainly going to pique people's interest."

But yesterday she appeared more cautious about the prospect of a pregnancy or engagement being revealed.

"It doesn't reveal the secret," she said. "I'm sure that's not true. It reflects on the hardback."

Even if Mr Burrell, 46, has chosen only to reveal lesser secrets, or merely to update the public on his life since publication of the hardback, the paperback is likely to shed more unwelcome publicity on the Royal Family.

He was mauled by the newspapers that failed to buy up the serialisation rights of the hardback, which sold one million copies in the UK and was sold in 13 countries.

Paperback sales usually outstrip hardback sales, and Mr Burrell is planning to push the new version with a book-signing tour.

Ms Gunn said: "For the hardback there was only a US tour, but for the paperback Paul will tour the UK and there will be signing sessions."

In retaliation for the new chapter, Princes William and Harry, who accused their former butler of "cold betrayal", were reported to have cancelled a meeting with Mr Burrell that was intended to clear the air after the hardback's publication in October .

A spokesman for Clarence House denied a meeting had been arranged and said: "This is his last shot and then we can move on. I think the public has made its mind up about Mr Burrell."

After next month's publication, Mr Burrell, who is estimated to have made up to £3m from the book but still runs a florist shop in Holt, near Wrexham, is unlikely to have anything more to say about the Royal Family.

But he is understood to have signed up with an American talent agency called The Firm in Los Angeles and is also considering a number of offers from television stations.