LONDON -- A book containing sensational allegations about a five-year love affair between Princess Diana and a dashing cavalry officer triggered a frenzy of media and public interest Monday.


Kept under wraps until the last minute, the book was dismissed by Buckingham Palace as "worthless and grubby" when it went on sale across Britain.


Called "Princess in Love," the slim volume alleges Diana and cavalry officer James Hewitt had romantic trysts at Kensington Palace, at Prince Charles' country seat, near the swimming pool at Diana's family house and at the home of Hewitt's mother.


"This is another grubby little book that does not bear wasting time on," a Buckingham Palace spokesman said.


Diana's lawyer called on the public to "show their contempt for those who seek to make money out of the unhappiness of the Royal couple".


Diana, 33, married Prince Charles in a fairy-tale ceremony in 1981 but separated from the heir to the throne in 1992.


But the book's author, Anna Pasternak, grandniece of "Dr Zhivago" author Boris Pasternak, was unrepentant. She said she was convinced of the truth of the allegations when Hewitt showed her his letters from Diana and wanted to tell the story in the most dignified and sympathetic way possible.


"The motive behind (the book) was not to make money, it was to get the truth across," Pasternak told ITN news. "I felt it was too beautiful a love to keep secret."


Written in the breathless, racy style of romantic pulp fiction, the book says it aims to "contribute to a proper understanding of and sympathy for Princess Diana".


The book, on sale for just under ?15 ($24), alleges a passionate romance between Hewitt and Diana from 1986 and 1991, a year before she separated from the heir to the throne. But it draws a modest veil over the most intimate moments.


Starting with riding lessons, their friendship grew until, after a dinner at Kensington Palace, the book claims Diana took Hewitt into her sitting room for coffee.


"Suddenly she could not bear it any longer, her need was too much. She was starting to flail. So, with the ease of a dancer, performing a well-worn routine, she stood up, walked across to him, and slipped sideways on to his lap. ... Diana stood up and without saying a word stretched out her hand and slowly led James to her bedroom."


Leaving the reader briefly outside the bedroom door, it resumes the story with: "Later she lay in his arms and wept."


The couple began to spend regular weekends together, which "sped by in a sybaritic haze of abandonment".


Britain's tabloid newspapers, took an unwontedly high moral tone.


The left-wing Daily Mirror, castigated Hewitt with the words: "He is a revolting creep. Horse-whipping would be too good for him."


The Sun, Britain's biggest-selling tabloid, called the 36-year-old bachelor "Major Rat" and said in an editorial: "Compared to Hewitt, even horse manure smells sweet."


But the newspapers' scorn did nothing to dampen public interest in the work. Bookseller Books Etc opened the doors of its central London shop 1 1/2 hours early to deal with the rush.


Hewitt, who newspapers said could net ?3 million from the book, was in hiding Monday with newspapers speculating he was on an Argentine polo farm.


Constitutional experts said it was theoretically possible, although practically unlikely, for both Hewitt and Diana to be charged with treason -- if the allegations were true -- which still carries the death penalty.