When Parliament House officials finished work on Thursday it was business as usual, but when they woke up on Friday they were at red alert.
On Thursday afternoon, Parliamentary Services boss Carol Mills batted away questions about security and breezily chatted about plans for the Parliament's struggling gift shop.
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By Friday morning, plans to have armed police walking the corridors had gone public, with Australian Federal Police officers to replace the unarmed public servants who have always provided internal security.
Prime Minister Tony Abbott said on Friday that Parliament House had been identified as a potential target through "chatter" intercepted by security agencies.
"There are close links between Australians fighting with ISIL in Syria and Iraq and networks of support back here in Australia, and the chatter involving Parliament House was chatter between Australians in Syria and Iraq and their supporters here in Australia," he said.
"In response, I spoke with the presiding officers. I commissioned an urgent review of security at Parliament House.
"On receipt of that review, I wrote immediately to the presiding officers asking them to implement this review.
"That implementation is now taking place and as a result of that review the Australian Federal Police will be in charge of not just the external security of Parliament House but the internal security as well.
"There will be armed Australian Federal Police present in and around our national Parliament at all times."
Mr Abbott predicted more inconvenience for visitors to the building.
"I regret the fact that in these times there will be an additional level of inconvenience from time to time to the public," he said.
"I regret the fact that buildings such as Parliament House will be a little more restricted in the future than they have been in the past, but the community expects government at all levels to keep them safe."
Just months ago, the Department of Parliamentary Services was mulling a plan to replace the AFP officers who patrol the building's grounds with private security guards.
The advice from security agencies was that the expensive high levels of security, in place since the days of the September 11 2001 attacks on the United States, were no longer necessary.
It was only two months ago that the Department of Parliamentary Services felt relaxed and comfortable enough to try to save a few bucks by allowing MPs, senators, their staff, families and friends, and federal departmental workers to enter without a routine security screening.
A week ago, The Canberra Times reported that a deal to finance the building's AFP security presence had still not been thrashed out, with the department and the police force still haggling over the price.
Ms Mills was unavailable for comment. But in language reminiscent of that surrounding the government's Operation Sovereign Borders, a spokesman for the Attorney General's Department said they would not talk about "operational matters".
"We are unable to comment further on Australian Parliament House protection matters for operational security reasons," he said.