For three years Barry O’Farrell has been an excellent premier of a state that desperately needed both good government and an end to the blatant corruption that became a feature of New South Wales Labor’s last years in power.

Like any politician, he was not above compromise and deal-making — his pandering to Legislative Council crossbenchers like the Shooters Party and Fred Nile was faintly sordid. The circumstances in which James Packer was given his way on Barangaroo — enabled by both O’Farrell and Labor — leave a particularly unpleasant taste in the mouth.

But O’Farrell got NSW back on its feet economically, even if he and Treasurer Mike Baird routinely overstated the fiscal task they had been left by Labor — the Iemma, Rees and Keneally governments might have been debacles but they kept their fiscal discipline. Prime Minister Tony Abbott likes to claim his is an “adult” government that will “under-promise but over-deliver”, but O’Farrell’s was the real thing. He projected an image of moderate reformism, intelligence and, above all, calm competence. He looked set for a long and successful premiership.

Now all that’s finished, brought undone by an inexplicable memory lapse over what will now be the most famous bottle of wine in Australian political history, a 1959 Grange delivered by Sydney business identity, Liberal fundraiser and Independent Commission Against Corruption star Nick Di Girolamo after O’Farrell’s 2011 victory. O’Farrell denied receiving it — or thanking Di Girolamo for it — to ICAC yesterday. Then O’Farrell’s thank you note, slightly pro forma but with a joke about the year (when O’Farrell was born), turned up.

O’Farrell either lied or forgot; he denied misleading ICAC today, and instead insisted he’d had a “massive memory fail”. Then he quit. There are few who will seriously entertain the idea that he lied: O’Farrell, in various shapes and sizes, has been an MP for nearly 20 years and always been a straight talker.

Politicians accepting responsibility and being consistent is an increasingly old-fashioned concept. From the Prime Minister on down, we’ve become used to politicians who believe statements they’ve made in the past are mere inconveniences, to be explained away or disregarded in the quest for political advantage. Other politicians may have tried to weasel out of it and conjure up a form of words to justify the lapse. To O’Farrell’s considerable credit, he accepted responsibility, reflecting a standard of ethics in public office far higher than NSW voters have had to endure.

“Now he’s gone after three years, and NSW will be the worse for it.”

It wasn’t supposed to be like this. The exposure of corrupt figures like Eddie Obeid and Ian Macdonald was supposed to, and did, inflict profound damage on Labor, so much so that the damage seeped through to the federal level. But O’Farrell’s government had its problems with former minister Chris Hartcher, who will play his own role at ICAC before too long. And the part-Obeid owned Australian Water Holdings had extended its tentacles into the Liberal Party via Di Girolamo, former staffers and, most famously of all, the “respected” and “admired” Arthur Sinodinos, who faces an extended stint on the Senate backbench after his singularly inept “I don’t recall” performance before ICAC.

With O’Farrell gone, Sinodinos should show some of the same decency and bail out too, and let his government appoint a proper replacement.

It all echoes, sometimes in uncanny parallel, the fate of Nick Greiner, another outstanding NSW Liberal premier brought undone by ICAC. Greiner established ICAC, and the assumption back then was it would damage NSW Labor, which had generated plenty of sleaze before voters turfed it out in 1988. Instead, ICAC terminated Greiner’s career early in his second term in a finding about his dealings with former Liberal-turned-independent Terry Metherell that he was “technically corrupt”. The finding was overturned (Greiner always argued his deal with Metherell was stupid, but not corrupt), but not before Greiner’s premiership was finished.

The key difference: Greiner was put in that position because, despite his landslide 1988 win, he was forced into minority government in 1991 in the backlash against his reforms and because of a cynical campaign by then-opposition leader Bob Carr. O’Farrell had learnt the lessons of Greiner’s time in office, and was in much less of a rush to implement the reforms NSW needs. Given the scale of his 2011 victory, it looked like O’Farrell would have at least eight years to get NSW back on its feet.

Now he’s gone after three years, and NSW will be the worse for it.

Maybe both sides will learn from this about the need for a much greater separation of politics — especially at the state level — and business: that the close relations between MPs, staffers, former politicians and staffers, party officials, trade unionists, fundraisers, lobbyists and business people on the make — par for the course throughout Australian politics at all levels — are deeply unhealthy. Unhealthy not just for the quality of government we get, but unhealthy politically. Just ask NSW Labor, which is now a byword for corruption.

Just ask Barry O’Farrell, who has paid the ultimate price.