It was then that the opposition leader was handed the 2011 letter of request he signed for a man who had only days earlier taken his place as one of the most reviled figures in Australian history – Lindt cafe siege gunman Man Haron Monis.

The office knew the discovery of the letter he signed for Monis in relation to a child custody matter – believed to be by a member of his Blacktown electorate staff – was political dynamite.

Robertson's instinct was for immediate full public disclosure – a view no doubt given weight by the fear the letter could surface with disastrous consequences during the election campaign in early 2015.

His staff also knew that because the letter was sent to the Department of Community Services, the government would eventually become aware of its existence. There really was no choice, they argued.

Besides, releasing the letter would allow Robertson to get on the front foot and announce its existence while explaining what he believed was the entirely routine nature of the document; that it was no more than a local MP's basic courtesy for a constituent. Or so the thinking went.

The timing for its public release was initially set for last Saturday, but legal concerns meant that shifted to 10am on Monday, a plan known only to a tight leadership group.

But by 9.30am on that morning details had leaked. Robertson's office began receiving calls from the media, demanding to know details.

Instead of being of the front foot, Robertson was left looking as though he was defending the indefensible.

Things moved extraordinarily quickly after that. Robertson's long-time critic, shadow treasurer Michael Daley, began phoning colleagues to push for a leadership change.

Previous attempts had failed, mainly due to reluctance by ALP head office to change leaders in the first term of opposition.

But on Monday it soon became apparent the mood was very different.

By Tuesday morning Robertson was put on notice that a group of his senior colleagues planned to visit him at 5pm that day with the intention of resolving the leadership issue.

Implicit in their message was this: if you don't resign, we will take steps to blast you out of office.

Half an hour before the deadline, Robertson held a media conference to announce his resignation.

After nearly four years in the opposition leader's job, he was to be denied the opportunity to contest an election at the last minute.

The NSW ALP, which had invested so much time and effort into its public rehabilitation after the toppling of former NSW Premiers Morris Iemma and Nathan Rees at the hands of powerbrokers Eddie Obeid and Joe Tripodi had removed yet another leader.

And this time there was not an Obeid or Tripodi in sight.

The NSW disease

Former Queensland Premier Anna Bligh famously labelled it the "NSW disease" – the willingness of the party to cut down its own leaders at the slightest hint of a drop in popular support.

The label was applied by Bligh after Labor's 2010 federal election narrow victory, preceded by the knifing of Prime Minister Kevin Rudd by Julia Gillard. This in turn followed the tearing down of  Iemma and Rees.

But in NSW, the closest parallel to the Robertson's downfall is in fact on the Coalition side.

In December 1998, three months before the state election that would serve as Labor Premier Bob Carr's first re-election test, the NSW Liberals cut down then leader Peter Collins in favour of Kerry Chikarovski.

It proved a disastrous move so close to the election; voters doled out a thrashing to the Coalition, which  – in yet another parallel – ran on a policy of privatising the NSW electricity network.

The Coalition would not regain power in NSW for more than a decade.

Does it therefore follow that the NSW Labor party, having deposed yet another leader so close to an election, can expect the same dividend in March 2015?

There is little doubt the switch is causing headaches within each party's head office. Carefully constructed campaign strategies hitherto focusing on selling Robertson as an alternative Premier and alternatively demonising him as a union thug have been binned.

The danger for Labor is that should the narrative about ongoing ALP disunity take hold – as the Coalition no doubt will try to ensure it does – it could serve as a timely reminder to the electorate why it turfed out Labor in the first place.

This would be disastrous, as it is a reputation Robertson and the NSW ALP have spent the past four years trying to counter.

To give him his due, Robertson as leader oversaw serious internal reforms, including new disclosure standards for his own shadow cabinet in a bid to regain voter trust.

Among other initiatives were 2013's federal intervention in the division by Rudd, which introduced new independent tribunals for party disputes.

Crucially, there was also the embrace, including by Robertson, of a new way to elect the parliamentary leader whereby the rank-and-file membership would be given 50 per cent of the vote alongside that of the caucus.

Ironically, this reform was designed to make it more difficult for powerbrokers within the caucus to depose the leader. (The model will not apply to the January 5 meeting as it is within six months of an election).

Now, all of this rehabilitation work is placed in jeopardy following Robertson's demise.

At the 2011 state election the Coalition sought to counter the "fresh face" of Premier Kristina Keneally with the advertising tag line: "Same old Labor, same old tricks". It would be unsurprising if this is reprised in 2015.

But Labor must also cling to the glimmer of hope that the choice of a new leader could in fact reinvigorate its election efforts.

This effect has been most recently evidenced by Premier Mike Baird's soaring popularity after he replaced Barry O'Farrell in April. What should have been a disaster in fact has become a blessing for the Liberals as Baird is embraced by the electorate.

With Robertson at the helm polling showed the ALP could fairly expect to claw back a respectable 15 seats. While still delivering an election loss, this would place it in a competitive position at the next election in 2019.

The problem for Robertson was that polls showed he was deeply unpopular. The latest Fairfax-Ipsos poll put his approval rating at just 35 per cent, with disapproval running at 37 per cent.

Some ALP strategists argue this was a natural state for any state opposition leader, given they struggle to gain any kind of visibility outside an election campaign.

The theory was that once his story could be shared, the electorate – and in particular Labor's base – would warm to him as a former electrician on a crusade to protect households from soaring electricity prices should the Liberals get their way and sell the the state-owned electricity assets.

But the fear that in part drove this week's successful push to oust him was that Robertson was simply the wrong man for the job. The evidence was that in four years he had failed to connect with voters.

These concerns were exacerbated by the perception that the Monis incident once again exposed Robertson's greatest weakness: poor judgement.

Going into an election campaign, this was viewed as a particularly serious problem.

His senior colleagues have acted on the latter view, meaning the key question for Labor remains: what kind of leader can instil internal confidence, while also winning back its electoral base?

The next leader

It's often said that the next NSW Labor premier is not yet in the Parliament.

But this is dangerously negative thinking and for now the party must believe that its next leader can take it all the way to the Treasury benches.

These are the issues Labor MPs will be mulling over the Christmas and New Year break ahead of a caucus meeting on January 5.

Should Robertson have held on until after March 28 next year, the party would have moved to an orderly leadership ballot as under party rules the position is automatically spilled after an election loss.

As last year's federal contest between Bill Shorten and Anthony Albanese demonstrated such a ballot allows Labor to present a positive, democratic face to both its own members and the wider public.

The decision to force Robertson's resignation has robbed Labor of this opportunity – for now at least.

It also potentially undermines the value of such a ballot after the next election: will members really be willing to dump a new leader after only three months in the job?

Indeed there are already signs that the leadership contest – shaping up as a choice between shadow Treasurer Michael Daley and environment spokesman Luke Foley – will be bitterly fought even before a single vote is cast.

General secretary Jamie Clements is understood to be expressing strong support for Foley, should he agree to stand.

Foley supporters point to his "consistent position" in opposing electricity privatisation.

The issue will be central to next year's election campaign, given the Baird government's proposal to lease 49 per cent of the electricity "poles and wires".

This is in contrast to Daley, who as the Liberal party has gleefully pointed out, helped sign off as finance minister on the sale of some electricity assets under the former Labor government.

Foley supporters also note Daley's role in pushing for Robertson's replacement – not necessarily the type of thing a new leader wants on their CV.

But Daley supporters point to Foley's former role as secretary of the Australian Services Union. They question the wisdom of electing another "union boss" to the leadership after Mr Robertson, who was previously secretary of Unions NSW.

With the backing of ALP head office, Foley must be viewed as favourite if he decides to run on January 5.

Additionally, a Foley candidacy would solve another headache for party leaders in Sussex Street: the bitterly fought preselection in the seat of Auburn.

Because he is in the upper house, the party will need to find him a lower house seat should he become leader.

The Auburn preselection is in limbo, with incumbent MP Barbara Perry levelling allegations of branch stacking at her challenger, former mayor Hicham Zraika.

Perry has taken the issue all the way to the party's review tribunal, which is not due to make a decision on the allegations until January 21.

Imposing Foley as the candidate in Auburn via the powers of the ALP national executive would also allow the party to cancel the preselection, nullifying the dispute between Perry and Zraika.

Meanwhile, gleeful Liberal MPs are describing the decision to cut down another leader as a Christmas present from the ALP. Labor, in turn, will be hoping for a happier New Year.