Ken may rue the day he got into bed with the 'Standard'

When Ken Livingstone stood up last week to lambast the Evening Standard he had no idea of the storm that was about to break.

The Mayor of London condemned the paper for what he called "one of the most inaccurate and distorted articles I have ever seen about myself". With hindsight, he might have wanted to adopt a more temperate tone.

What incensed Mr Livingstone was a series of articles that began with the revelation his girlfriend and office manager Emma Beal, a former employee of the Evening Standard, was expecting his child. This was followed by a story of a fracas at a drunken party at the north London home of Ms Beal's sister. Mr Livingstone was accused of manhandling Ms Beal and being involved in a "tussle" that resulted in Robin Hedges, an art editor on the Evening Standard's ES magazine, being taken to hospital.

The problem for Mr Livingstone in trying to keep a lid on the incidents at the party was that the Evening Standard was not just reporting the story; its staff lay at the heart of it.

To tell the full story from the beginning it is necessary to wind the clock back to 1996 and the start of Mr Livingstone's stint as the Evening Standard's restaurant critic. When Adam Edwards, then editor of ES magazine, was unable to make an appointment for lunch with his prospective restaurant critic, he sent his personal assistant instead. And that's how Emma Beal met Ken Livingstone.

Four years later, Mr Livingstone, following his election as mayor, handpicked Ms Beal to run his new office. Then in May this year, the Standard broke the first of its scoops. On 30 May, it reported that Ms Beal, 34, was pregnant after she and Mr Livingstone, 56, holidayed in Australia.

The next day things began to hot up for the Mayor. It is understood the story of Ms Beal's pregnancy prompted two phone calls to the Standard. The callers told a remarkable tale of a drunken party that had taken place on 19 May at the north London flat owned by Ms Beal's sister Kate.

The race was on to go to press before the Jubilee bank holiday weekend. "Mayor and Reveller's Mystery 12-ft fall" ran the headline on 31 May for a story that told how Mr Hedges had tried to intercede when the Mayor remonstrated with his girlfriend for smoking. "Minutes later," claimed the article, "he was found at the bottom of the stairwell." Mr Hedges told the newspaper: "Emma is my closest friend and I don't want to do anything that might upset her." By last week all that was turned on its head. Some sources suggest the Mayor's office made a serious error in failing to keep Mr Hedges "onside".

Mr Livingstone says the Evening Standard put pressure on Mr Hedges to change his story and corroborate their scoop. Mr Hedges says he was cajoled into making the statement exonerating Mr Livingstone. So when the Mayor made his attack on the Standard at the GLA meeting last Wednesday, the newspaper's response was swift and savage. On pages one, four and five the next day Mr Hedges gave his own account. The upshot is a police investigation and a GLA meeting this week that could lead to Mr Livingstone being stripped of his powers.

The Mayor says he drank no more than three glasses of wine in seven hours and maintains the newspaper's coverage is a vindictive, malevolent attack. The question now is: where do the Standard and the Mayor go from here? According to the rumour mill there remains "one more killer revelation" to come out of the affair.