"I turned on the television and within minutes others from my office and the Federal police Commissioner rang me to explain what was happening," Mr Howard recalled this week, on the eve of that fateful day on April 28,1996.

Thirty five people, mostly tourists visiting the historic Tasmanian site, had been killed at the hands of a man armed with semi-automatic weapons.

"Later that day the premier of Tasmania, Tony Rundle, rang me. Even at that early stage we talked about the possibility of tightening the gun laws," he recalls.

The tragedy would be both a tremendous challenge, but also a moment that defined Mr Howard's leadership and his prime ministership. Strong. Determined. Practical.

"How did I react? I immediately focussed on what I could do. It seemed to me that I had to do something big because it was such an awful tragedy," he said.

"The reality in politics is you have a certain amount of political capital. It will go. It will either go through inactivity and waste or you expend it on something worthwhile."

The country, he said, was reeling. "It couldn't believe that something of this magnitude could happen in Australia. I thought, I have this huge majority, we have elected a new government and we have to do something."

He flew to Tasmania, with Labor leader, Kim Beazley and Democrat leader, Cheryl Kernot to attend services and lay a wreath at Port Arthur. He met with the traumatised emergency workers who had to deal with the shattered bodies of the 23 wounded.

But front of mind for Howard was how to prevent such a tragedy ever again.

What followed was a concerted effort led from the top to ban the importation and sale of automatic and semi-automatic weapons in Australia.

Breaking the gun culture

Gun laws are primarily a state matter. The federal government has control only over importation, which meant Mr Howard had to convince all the states and territories to embrace consistent laws which he would propose.

"I thought if ever we were going to do something dramatic and lasting to change Australia's gun laws to prevent the emergence of a more alien gun culture in our country, this was the time to do it," he said.

The federal government worked with the states to buy back the banned weapons and any weapons people no longer wanted, with nearly 700,000 handed in. For its part, the Federal government  increased the Medicare levy to pay for "buyback".

New consistent laws on licensing and storage of legal weapons were introduced by all the states. People who needed guns for their livelihood had to be licensed and their weapons registered and guns needed to be stored in a locked cupboard, unloaded.

Within days of the Port Arthur massacre, the police ministers met in Canberra, at a meeting hosted by the then Attorney-General, Daryl Williams.

"It was difficult for my National Party colleagues. It was particularly difficult for the National Party leader in Queensland, Rob Borbidge. There was resistance in Western Australia, I think as much on states' rights' grounds as on anything else," he said.

"Daryl had a meeting with the police ministers and then he brought them all round to my office. I had made a point of being in Canberra that day, in reserve, so to speak. I thought it might be necessary to talk to the police ministers, and I did," Howard said.

As Prime Minister, he was the person who had to sell the reforms to the public, and in rural Australia there was deep anger that their gun ownership would be curtailed because of a madman in Tasmania.

After receiving death threats just before he spoke at a rally at Sale in rural Victoria, Howard's advisers recommended he don a bullet proof vest before he spoke. It was a decision he said he regretted as he did not feel unsafe.

Soon television screens were filled with pictures of huge piles of weapons being dismantled and crushed.

"I don't believe we were on the cusp of going down the American path," Howard said. "But I do think the gun laws have had the practical value of reducing the mass slaughters. There were 13 before the new laws; and if you define such an event as five or more victims,  there have been none since.

"Surveys indicate it had a big impact on male youth suicide. I believe we have prevented a lot of death of people who would once grab hold of a rifle.

"The simple reality is it is easier to kill 10 people with a gun than it is with a knife or a hammer or something else. I also think the community believes this is something of a demonstration to the rest of the world and that they might follow our lead."

For his part in making Australia safer, Mr Howard has been personally vilified by the National Rifle Association, the powerful US gun lobby. In the current presidential campaign the NRA is again running ads claiming that Australia's laws mean taking away people's guns and making gun ownership a crime  - without distinguishing between the ban on semi-automatic weapons and rights to still own guns responsibly.

As prime minister, Mr Howard  had brief discussions with then President George Bush and Secretary of state, Condoleezza Rice, but said their experiences and the US's history made the discussion a difficult one.

Asked what he would say to the current presidential hopefuls, Mr Howard said he would simply explain what he had done, and the results.

"I would not presume to lecture the American candidates. I would just point out that we are a safer country, and I would say I understand what a terrible burden gun deaths are on black America. Black males make up 6 per cent of the US population, yet they comprise 46 per cent of gun related homicide," he said.

"Americans will often say to me there are so many guns in circulation the only way the good guys can protect themselves is to also have a gun. Now I think that is a stupid argument myself."

Mr Howard estimates that the gun buyback in Australia was the equivalent of taking 30 to 40 million guns out of circulation in the US.

Twenty years on

Twenty years on Mr Howard said his gun laws have stood the test of time.

"You might argue that laws allowing hunting in national parks [in NSW] have slightly watered things down but not to a significant degree. The police think there are too many handguns. That's a matter for state governments," he said.

He also queried whether an amnesty to allow handguns to be handed in would have much effect, given that most of the illegal weapons are in the hands of criminal gangs.

But there are pressures.  A 2012 Crime Commission report, which was not publicly released was quoted by then police minister, Jason Clare, found there were 2.75 million registered guns in Australia held by 730,000 licence holders.

But it also estimated that conservatively there were 250,000 long barrel guns and 10,000 handguns in the illegal firearms market. One such unregistered weapon, a 1953 shotgun found its way into the hands of the Lindt cafe gunman, Haron Man Monis.

The ban on the importation of the Adler lever action shotgun capable of rapid multiple fire is due to expire in August.

Nonetheless, Australia's action on gun control remains one of Mr Howard's greatest legacies.

"It was an example where the government took advantage of a horrific incident to bring about a major change. I am very proud of it," he said.

The Sydney Morning Herald