Clinton accused: The secret recordings which tell of sexual encounters next to the oval office

If President Clinton falls, history will record that the woman who brought him down was not Monica Lewinsky, but Linda Tripp, a matronly, middle-aged former White House secretary with whom he never even contemplated a sexual relationship. The appropriately named Ms Tripp, John Carlin reports, was the spy in the White House of love.

She was a spy and a detective, a seemingly bluff, business-like Miss Marple figure whose cunning, trickery and fierce single-mindedness lulled the President's chief accomplice into telling all.

Had Ms Tripp not insinuated herself maternally into Monica Lewinsky's graces, winning her absolute trust, it is likely that the young college graduate would not unwittingly have spilled the beans about what she claims to have been an intense affair with the President. Without the 20 hours of taped conversations with Ms Lewinsky that Ms Tripp secretly recorded last year, Kenneth Starr, the special prosecutor investigating the president, would not be in possession now of by far the most damaging evidence he has accumulated in four years of relentless toil.

The tapes tell of sexual encounters in a study next to the Oval Office, of feverish midnight phone calls, of Ms Lewinsky's progress from star- struck infatuation to confusion, tears and dejection, yet of her determination to do the honourable thing and lie to protect the man she came to call "the creep" and "the big he".

"I will deny it so he will not get screwed in the case," she says on one of the tapes, obtained by Newsweek magazine. "But I'm going to get screwed personally." Saying at one point that Mr Clinton was "in denial" about his relationship with Paula Jones, the clearly tortured Ms Lewinsky said that she could not find it in herself to betray her paramour. Sticking with "the cover story", she says, "is what I signed up for when I began the relationship". And then she adds she is desperate that Mr Clinton not find out she blabbed about the affair. "If I do that," she moans, "I'm just going to f---ing kill myself."

Thanks to Ms Tripp, Mr Starr now has these recordings and several others said by some who have listened to them to be shockingly graphic in their description of the relationship that Mr Clinton insists on saying was not "improper". The evidence suggests strongly, however, that Mr Starr has ample evidence to demonstrate that Mr Clinton had a sexual relationship for more than a year with an attractive, evidently impressionable 21-year- old woman who caught his eye in 1995 when she arrived at the White House on a work-experience basis. Thanks to Ms Tripp, who turned up at Mr Starr's office with her devastating evidence only 12 days ago, the special prosecutor is potentially armed now with the legal weaponry to charge the president not only with perjury, but with coercing Ms Lewinsky to commit perjury. For, never mind the question of Mr Clinton's raging libido, Ms Tripp's tapes indicate that he, in collusion with his friend and Washington power lawyer Vernon Jordan, persuaded Ms Lewinsky to lie under oath to Paula Jones's lawyers on 7 January that she had never had an affair with the President.

If the perjury allegations turn out to be true Mr Clinton will be impeached and may find himself seeking refuge in ambiguous constitutional statutes regarding presidential immunity to try and avoid the prospect of criminal prosecution and a possible term in jail.

The unlikely friendship between Ms Tripp, 48, and Ms Lewinsky, 24, flowered in 1996 at the Pentagon, where they worked in adjoining offices. Ms Tripp, who had worked in the Bush White House, left for the Pentagon in 1994 after a succession of prickly exchanges with Clinton staffers. She had antagonised the White House by testifying in Congress about the curious circumstances surrounding the death of Vincent Foster, the senior White House aide who committed suicide, and about the embarrassing Travelgate affair.

More than a year ago, towards the end of 1996, Ms Lewinsky began confiding to Ms Tripp about the affair she said she had with the President. According to testimony Ms Tripp has given Mr Starr, Ms Lewinsky told her that mutual attraction blossomed into a full-blown affair in November 1995, a month before she was given a full-time job at the White House. Ms Lewinsky told Ms Tripp of her vivid recollection of a White House party in mid-November 1995 where, wearing a revealing dress, she made teasing eye-contact with the President. In an echo of Paula Jones's testimony about her first encounter with then Governor Clinton in 1991, it was a short step from eye-contact to sexual arousal. Shortly after the party the affair began. The sexual encounters, which continued periodically during most of 1996, when Mr Clinton's energies were otherwise engaged in his re-election campaign against Bob Dole, took place mostly in late afternoon and on weekends, only occasionally late at night.

Ms Tripp did not start taping her conversations with Ms Lewinsky until last summer. What prompted her was her fury at comments by Mr Clinton's personal lawyer, Robert Bennett, that she was a woman who was "not to be believed". Mr Bennett's comment came in response to an allegation by Ms Tripp that she had seen another White House aide, Kathleen Willey, emerge from a meeting with the President with her make-up smeared and her clothing rumpled. The truth of Ms Tripp's allegation was apparently confirmed when Ms Willey told Paula Jones's lawyers under oath that during the meeting the president had suddenly grabbed her, kissed her and groped her, saying, "I've always wanted to do that."

Ms Tripp might have been vindicated but her rage at Mr Bennett's remark was unabated. Determined to salvage her name, she began secretly taping her telephone conversations with Ms Tripp.

On Monday 12 January Ms Tripp delivered the tapes to Mr Starr who asked her if she would agree to meet with Ms Lewinsky in person and record the exchange with a body wire. On 13 January, with the collaboration of the FBI, Ms Tripp did just that for four hours in a hotel across the Potomac river from Washington in Arlington, Virginia. There it was that Ms Lewinsky confessed that she lied to Paula Jones's lawyers in the sworn affidavit she gave them on 7 January. And there, reportedly, details emerged of the discreet role Mr Jordan had played in persuading her, on the President's behalf, to lie about the affair.