For many years, Linda Tripp was a dutiful military wife who followed her army husband around the globe, a civil servant so trusted that she landed several sensitive military jobs, including a classified position with the highly-secret Delta Force.

But more recently, after a lengthy stint as a White House aide, Ms Tripp became enmeshed in very different circumstances, as a recurring figure in several ongoing inquiries surrounding President Clinton.

She has been called to testify about Whitewater and the suicide of deputy counsel Vincent Foster. Now she has become a key source of information about two sexual encounters Mr Clinton is alleged to have had, the latest of which has spurred perhaps the most serious investigation to confront his Presidency.

She even began writing an "insider's" book about White House intrigue not long ago, but abandoned it because she feared it might ruin her Washington career, according to a friend and former colleague.

"She really agonised over the benefits and the downsides" of writing more than the couple of chapters she finished with the help of a ghost writer, he said. "She said to me, `What's a few thousand dollars compared to throwing away a career?' "

As the news that Ms Tripp secretly tape-recorded conversations with Ms Monica Lewinsky emerged this week, her motives have become a central but unanswered question.

Was Ms Tripp out to get material for the book? Was she trying to protect her job after Mr Clinton's lawyer, Robert Bennett, accused her in public of lying when she told Newsweek about another woman alleged to have had an affair with Mr Clinton? Did she develop a personal vendetta against Mr Clinton?

The image of Ms Tripp being revealed is filled with contrasts. Some of her friends and colleagues are wondering how it is that somebody they consider an honest and hard-working executive assistant, who once showed enthusiasm for Mr Clinton, has become the primary channel for such inflammatory allegations against him.

Yet in recent days some White House officials have characterised Ms Tripp as an indiscreet gossip whose loyalty they came to doubt.

Ms Tripp's sudden splash into public view, as a woman at the epicentre of a presidential scandal, willing to secretly tape a friend from work during 20 hours of conversation, seems a far cry from the placid life she once led as a military wife.

For 10 years, beginning in 1972, Ms Tripp followed her husband around the world by finding jobs to match his roving assignments.

She worked as an executive assistant to the top-ranking military representative in the Netherlands, and as an aide to a senior official at the 7th Army headquarters in Heidelberg, Germany.

In 1987 she became a secretary in a classified unit of the US Army Intelligence Command at Fort Meade and a year later worked in the headquarters office of the army's Delta Force in Fort Bragg, North Carolina, according to a copy of Ms Tripp's resume on file at the Defence Department.

The Delta Force is a team of commandos trained to conduct covert operations.

In 1990 she began a White House career that lasted four years, first for President Bush and later for Mr Clinton.

Though her chores changed, she always worked close to the inner circle of advisers for both presidents.

She started there in the equivalent of the typing pool. Colleagues remember her as a straight person who kept confidences.

Ms Tripp's 21-year marriage ended in divorce in 1992. She now lives in Columbia, Maryland, with her two children and several cats.

Ms Tripp's account of her White House work, detailed in a 1995 deposition she gave to Whitewater investigators, suggests that she had arrived with ambition but left dejected, with little work to do and the strong sense that she was being shown the door.

In the Bush White House she worked her way up to the chief-ofstaff's office, in a role that she once described as a "jack-of-all-trades", managing files and phone calls.

Shortly after Mr Clinton's election, Ms Tripp recalls in the deposition, she believed her days in the White House were over. But a former Bush aide recommended her to Mr Clinton's transition team, and for the first three months of his term she worked on the support staff of Bruce Lindsey, one of Mr Clinton's closest advisers.

She moved to Foster's office, where, among other things, she was entrusted with photocopying Mr Clinton's tax records.

After Foster's suicide, and after the departure of White House Counsel Bernard Nussbaum, for whom she mostly worked, Ms Tripp's role changed drastically. In her deposition, she describes sitting at an empty desk in an obscure office for weeks with nothing to do "but prepare my resume".

When she returned from a threemonth leave, in August 1994, Joel Klein, an official in the counsel's office, told her there was no work for her at the time, or any on the horizon.

"It was never `You must leave'," she said in the deposition, "but the inference was, `Find something else.' "

White House officials found her a job in the basement of the Pentagon, just below the office were Monica Lewinsky would later come to work.