Among the worst government decisions in Australia's history, two were made that year by the Howard cabinet - the decision to go to war in Iraq and the decision not to put a price on carbon or do anything much about reducing greenhouse gases.

The reason the decisions were so bad, of course, was precisely because neither of them were real decisions of the cabinet, but personal decisions imposed on his cabinet by prime minister John Howard

The war decision was made apparently without debate. The carbon decision was made contrary to the opinion of nearly all senior members of the cabinet and their departments and of the Department of Prime Minister and Cabinet itself.

Critical documents on the war decision have gone missing, so the full story is yet to come, but the cabinet minute published on January 1 under the 20-year rule says the March 18 decision by cabinet to sign off on going to war was based on "oral reports by the prime minister".

Not included in the released documents were those of the National Security Committee of Cabinet - apparently the key driver of the decision.

But Howard took the matter to the full cabinet for endorsement and they complied like sheep without any back-up documents on risks; validity of the intelligence Saddam Hussein had weapons of mass destruction (which we now know he did not); the legality of the decision; or the need for a specific UN Security Council resolution.

The full cabinet went along with it on Howard's say so because Howard had been talking to US president George Bush and UK prime minister Tony Blair.

The minute said Howard had briefed his ministers on his "extensive discussions over a period of time" with Bush and Blair "concerning the disarmament of Iraq of weapons of mass destruction and the possible use of force against Iraq if it failed to disarm".

Howard told the cabinet he had received a call from Bush earlier the same day to formally request "Australia participate in military action by a coalition to disarm Iraq of its weapons of mass destruction".

It was decision-making at its worst, resulting in consequences at their worst.

The lesson is the more centralised and autocratic a government gets, the worse its decision-making becomes. Clearly one person cannot be right all the time. Without the challenge of contrary views - and importantly the opportunity for them to be put without fear of reprisal - the less chance a government has of getting things right.

Howard's government was notoriously centralised. One of his first actions on coming to office in 1996 was to remove six departmental heads. Throughout his tenure as prime minister, dissent of any kind, let alone floor-crossing, was career-truncating. Power was centralised in the prime minister's office.

So, in March 2003 Howard and a few members of the National Security Committee could easily get a rubber stamp from the full cabinet.

It obviously emboldened him. Come September and the carbon decision it was Howard on his own against all the senior ministers and main government departments.

All their research, analysis and opinion was overridden by Howard on his own after some conversations with industry leaders.

You can see Howard being impressed and duped by industry leaders to act against the national interest and stymie carbon pricing.

But the best advice (agreed upon by all the key ministers) was that carbon pricing was the most efficient way to reduce emissions. It remains so to this day. Howard's abrogation of the cabinet process and the spinelessness of the senior ministers at the time resulted in two decades of wasteful wrangling and (ironically) industry uncertainty because of government by winks and nods and insider direct lobbying to the prime minister, rather than proper processes.

Those 2003 decisions and Howard's big win in the 2004 election cemented dangerous centralisation as the exemplar of effective government. It is not. Ultimately it catches up.

The centralised "captain's pick" style of government was championed by Abbott, again with appalling results. The 2015 knights-and-dames captain's pick is a classic example of the importance of cabinet government and of giving ministers in the cabinet freedom to discuss and dissent on condition they collectively accept the outcomes.

In 2015, cabinet ministers woke up to find the decision made without their knowing. It did not profoundly affect the governance of Australia but ultimately it corroded the government through one of the most damaging forces in politics: ridicule.

We should be able to learn as much from occasions of the breakdown of good government as we can from when government is effective.

Surely, a big lesson of the 2003 Iraq War is that if too few people are making such an important decision they can be led astray. Parliament should legislate that cabinet cannot send Australia into war without parliamentary approval. Sure, that might only happen if the holders of the balance of power in a hung parliament demand it, but it would improve decisions.

The other lesson is one of accountability. Before the Hawke government introduced the 20-year rule, there was a more limited release of cabinet paper after 30 years. The reasoning was that by then, all the players would be dead or retired and well past embarrassment age.

But surely potential future embarrassment helps keep leaders in check. It is an accountability factor. That makes the case for an earlier release of cabinet documents - say 10 years, as in the ACT.

That time frame might make prime ministers more mindful of the need and usefulness of robust cabinet processes.