It took Martin Bryant a little more than half an hour to kill 35 people and wound another 23, wielding two semiautomatic rifles to wreak carnage at Port Arthur on April 28, 1996.

Just 12 days later prime minister John Howard — only six weeks into the job — announced the most comprehensive crackdown on gun ownership in modern Australian history.

It was arguably Mr Howard’s finest moment as prime minister, a reaction lauded even by his enemies on the left of politics, and an example still cited by gun control advocates in the US and elsewhere.

The Cabinet papers from 1996 that document the Federal Government’s response to Australia’s worst mass killing by a single shooter, released for the first time by the National Archives, do little to reflect the national trauma caused by the shooting spree, nor the enormous political pressures released by Mr Howard’s decision.

What the papers, to be released by the National Archives today, do reveal is a government that was united, determined and disciplined from the start.

Mr Howard learnt of the tragedy by a phone call from his press secretary, Tony O’Leary, as it was happening. He turned on the television to watch events unfold even before he was briefed by the Federal Police commissioner and senior members of his office.

Cabinet had a briefing the next day, in part from social security minister Jocelyn Newman, noting the Tasmanian government — long a loud voice of opposition to attempts at national gun reform — had agreed to a ban on semiautomatic weapons and to compulsory gun registration.

By May 6, Federal Cabinet had agreed to a package banning automatic and semiautomatic firearms, establishing the first real national firearm registration system, and funding the gun buyback that took nearly 700,000 guns out of the community.

Even then, opposition was brewing. Premier Richard Court had ruled out ceding WA’s right to make gun laws to the Commonwealth, as NSW had proposed.

WA police minister Bob Wiese, a Nationals MP, declared his opposition to the semiautomatic ban on the same day Federal cabinet met, clashing with police commissioner Bob Falconer over exemptions for farmers. But Mr Howard won support for the package on May 10, after a six-hour meeting with State and Territory police ministers.

The WA government continued to quibble over the details of the laws until November, and they caused political turmoil in regional Queensland — Mr Howard said last month they contributed to the “insurgency” that led to Pauline Hanson’s One Nation — but there is little sign of that in deliberations of his Cabinet.