Those poor choices apparently included his pillow talk with the 26-year-old postgraduate student from Newtown whom he met in mid-March at the Art Gallery of NSW. Kate says he told her all about his ambition to oust Nathan Rees - a ''freckle-faced Latham'' - from the leadership. After an affair lasting almost six months, Kate now doubts whether he has the character for the job: ''If he is capable of lying to his wife and children … why wouldn't he do that in other aspects of his career?'' On August 5, she called it off, having given up hope that Della Bosca would leave his wife, the federal Labor MP Belinda Neal. Last night there was no sign of Kate at her home in a converted Victorian terrace. But last Wednesday she decided to go public and phoned The Daily Telegraph. She felt betrayed and was angered by the fuss about Della Bosca plotting to take the premiership. At the same time, however, Channel Nine's Kevin Wilde was preparing a story for that night's news - Kristina Keneally, not Della Bosca, would seize the premiership on Monday.

That story proved to be wildly speculative. Della Bosca had no idea that Monday would bring a much bigger bombshell. About 5pm that day, the Telegraph's editor, Garry Linnell, called the minister and requested a meeting. ''He said, 'Should I be worried?' '' Linnell told the ABC's 7.30 Report last night. ''I said, 'I would just like to see you.' '' They met in Della Bosca's office and he listened, stunned, although Linnell said he endured the process with ''an enormous amount of dignity and grace''. That night, Rees says an adviser called him to warn that the story was about to break. Half an hour later, Della Bosca phoned Rees and offered his resignation. The Telegraph's story did not name Della Bosca's former lover. She appeared in a silhouetted photograph. But she volunteered that she had found Della Bosca ''hot'' and ''sexy''; that they entered Parliament House without security checks or signing the visitors' register, then had sex on a couch in his office; that she fell in love with him; and that ''he kept telling me he was going to leave his wife''.

At his news conference, Della Bosca was asked if he believed he had been set up. He paused for seven chilling seconds, then answered with apparent sincerity: ''There is no possible way in which anything that has occurred could be described as a set-up … I have to take responsibility for those poor personal decisions.'' But what was Della Bosca thinking? Who, amid a backroom campaign to become premier, would enter into an affair with a woman half his age? Who would leave a trail of text messages? ''Boy oh boy am I in love with you,'' he said in one. Who, if they were Della Bosca, a year after he had resurrected a career shattered by the Iguanas affair, in which he and his wife had been accused of abusing nightclub staff, would do such a thing? ''I didn't think he would be that stupid,'' said the president of the Labor Party's Brooklyn, Mooney Mooney and Lower Hawkesbury branch, Bob Brownrigg. Della Bosca refused to respond to ''personal matters''. But he insisted he breached no ministerial or security protocols. It is understood MPs are allowed to take family and friends into Parliament House without signing them in. The Speaker, Richard Torbay, is seeking clarification from the head of security. Linnell says the woman was ''definitely not a stripper'', as had been reported. He told ABC radio: ''She made it clear to us from the start that she did not want any money. She was very angry.''

Della Bosca was surely angry, too. He contained it. ''I've taken my medicine, I have to live up to my poor decisions.'' He regretted the ''embarrassment to my colleagues, my friends, my community, my church and my family''. A Catholic and an old boy of De La Salle at Cronulla, he said he did not want to pass judgment on the woman for going public. Rees had the same approach to Della Bosca. ''I'm not going to make moral judgments,'' he said. What about the unkind things the woman says Della Bosca said about Rees? Loading ''It doesn't matter,'' the Premier said. ''It's immaterial.''

with Ellie Harvey and Erik Jensen