Inside the last hours before Glady Berejiklian resigned as NSW premier

Gladys Berejiklian didn't see the end coming until a bombshell email landed on her desk and sparked hours of tearful meetings leading to her resignation.

Huddled with her closest allies and friends, the NSW premier almost decided to defiantly weather the storm before she ran out of options.

Then at 1pm on Friday she stood up in front of TV cameras and, barely holding it together, announced she was stepping down and quitting parliament.

Disaster came suddenly. Just a day before she was 'happy and in high spirits', according to one of her ministers.

Then on Thursday afternoon her office was notified that the Independent Commission Against Corruption would be investigating her over her dealings with her disgraced ex-boyfriend Daryl Maguire MP.

The curveball was quickly communicated to Energy and Environment Minister Matt Kean, who received three calls and a text from the spiralling premier. 

'Matty, it's urgent,' the text from his boss read, the Daily Telegraph reported.

Ms Berejiklian summoned her senior allies in her office and began to consider her options, strategising with Mr Kean, Health Minister Brad Hazzard and her closest friend Customer Service Minister Victor Dominello over the phone.  

Terse deliberations continued well into the night, with the premier pulling out of a virtual Town Hall meeting of 1,000 party members that evening.

The premier also postponed a crisis cabinet meeting scheduled for 11am to 4pm as she weighed up her options. 

Helping to guide the popular Liberal leader to a decision was Mr Dominello, considered one of Ms Berejiklian's most trusted friends and advisors. 

Ms Berejiklian went to bed on Thursday night planning to 'ride it out', a source close to the premier said.

The premier and her three top allies reconvened at 6.30am on Friday and walked through the options again, having slept on them.

After hours of deliberation, her initial determination to carry on floundered against the hard reality that even if she stood aside until she was exonerated, as Neville Wran did for 74 days in 1983, her position was untenable.

The inquiry could take weeks but it could also drag on for years, and with NSW days away from emerging from lockdown, the government and the state couldn't afford the distraction. 

After finally arriving at the tearful decision she would resign, Ms Berejiklian told her family and prepared a speech. 

Moments before her 1pm press conference, the fallen leader personally notified Treasurer Dominic Perrottet and Deputy Premier John Barilaro.  

'I've had to make a difficult decision overnight,' Ms Berejiklian said on Friday as she hastily read a prepared statement before refusing to take questions.

'It pains me to announce that I have no option but to resign from the Office of Premier. 

'I am extremely confident that whoever succeeds me will be more than capable to continue this job. Please give them your trust and confidence.