By Nick Assinder
Political correspondent, BBC News
It lasted 16 months, cost £1 million, saw senior Downing Street aides arrested and even then prime minister, Tony Blair, interviewed by police.
Lord Levy always denied any wrong doing
Yet the Crown Prosecution Service has now decided it will not be bringing any charges in the cash-for-honours probe - although this is certain not to be the end of the questions.
The result has come as a huge relief to all those at the centre of the probe, although all of them - from Tony Blair down - always maintained they had done nothing wrong and had nothing to worry about.
And it will bring to a close one of the darker episodes which marked the final year of Mr Blair's premiership and which appeared to contribute to a general sense of distrust in politicians and the political process.
But the inevitable recriminations and demands for answers about how and why this ever took place will start in earnest.
Some of those questions were hinted at by the man who led the inquiry, John Yates, the deputy assistant commissioner at Scotland Yard, who said it had been the Crown Prosecution Service's decision not to go to court, not his.
He also said the investigation would have ended sooner had he not been forced to widen it to cover the possibility there had been a cover-up.
Those remarks will lead to some serious probing over coming weeks but there will also be questions over what the entire episode achieved, what motivated it in the first place and whether it was a mammoth waste of police time and taxpayers' money.
Mr Yates said he had "significant material"
Mr Yates, who last November said he had "significant and valuable material" in the inquiry, is facing many of those questions, but so too are the media and the politicians who made so much of the affair before the police inquiry was concluded.
Speaking immediately after the announcement, Mr Blair said he knew it would end as it had and he offered no criticism of the police.
His friend and fundraiser, Lord Levy, expressed his disappointment at the way there had been constant leaks to the media which had been "misleading, factually inaccurate and personally damaging".
He refused to point the finger at anyone in particular but his words raised the question of whether either he or others may decide to pursue the issue either legally or otherwise.
It is certainly the case that the Commons committee which had already been examining the issues at the heart of this affair would now continue its inquiries there may be others.
Mr Yates has the defence that he was bound to pursue the case once such serious allegations had been laid by an MP and, as he said himself after the announcement, the investigation needed to be "thorough and meticulous in every respect".
It was certainly that, and prime minister Gordon Brown has said it was right to carry it out.
When SNP politician Angus MacNeil first asked the police to investigate allegations peerages had been offered for secret donations to Labour, few believed the affair would go very far.
After all it has long been an accepted and relatively un-controversial practice that supporters of and donors to parties often ended up in the House of Lords which is, after all, a political chamber.
The difference this time, however, was the suggestion that peerages were being blatantly "sold".
It was always believed that this was a fine line and that it would be hugely difficult to prove it had been crossed.
And all concerned, including Mr Blair, insisted there had been no wrongdoing.
But as the investigation dragged on, things took another turn when it appeared police were also looking at a possible cover-up.
The speculation then was that, just as with the famous Watergate scandal in the US, it was the cover-up that would lead to real trouble for those involved.
But that too proved fruitless and now the CPS has decided it should go no further.
In the intervening period, 136 people were interviewed, including Mr Blair and former Conservative leader Michael Howard, four were arrested including two of Mr Blair's closest aides, Lord Levy and Ruth Turner and press speculation over who might end up in the dock ran rife.
And, of course, the whole thing played into the public perception of politics and, particularly, the Blair administration's style of government.
The former prime minister was clearly both frustrated and angry that he faced what many saw as trial by media over this affair during his final months and could do nothing to answer back.
It is even possible that the speculation surrounding the affair hastened his premature exit from Downing Street.
It certainly cast a long dark shadow over his final period in office and proved a recurring distraction from other business.
Aides, including Lord Levy and Ms Turner, will also have reason to feel some resentment at the way they were subjected to widespread speculation about their roles.
The post-mortem and recriminations will now start in earnest and undoubtedly see many allegations thrown around about the motives and alleged political games played over the affair.
There will be demands for further inquiries into the handling of the investigation, the media's role in it and whether the case should ever have been pursued.
And, inevitably, it will add fuel to the debate currently raging about both the way political parties are funded - with demands for some level of state funding - and political patronage, particularly the appointment of peers.
Perhaps more importantly, however, will be the desire to restore some of that trust in politics and politicians - something Gordon Brown has already placed near the top of his list of priorities.