Australian Federal Police says that right up to 2pm, they had no reason to believe there would be trouble at an Australia Day event.
But there was trouble when a group of protesters marched on the nearby Lobby Restaurant in Canberra, sparking a security scare involving Prime Minister Julia Gillard and Opposition Leader Tony Abbott.
Australian Federal Police commissioner Tony Negus told a Senate committee on Tuesday that when the Australia Day function began at the restaurant at 2pm, all was quiet.
'Hindsight is a wonderful thing,' he told the estimates hearing at Parliament House in Canberra,
'However, there was no indication right up to 2pm when the prime minister and Mr Abbott arrived that anything would go awry.'
Asked about the wisdom of approving a prime ministerial event at a venue so close to the tent embassy, Mr Negus said the AFP didn't choose the location and was only notified about it on January 23.
Officers conducted a security inspection on January 25.
'Assessments were made by trained professionals in this area. We had people on the ground and uniformed police from ACT assisting,' he said.
Mr Negus said Ms Gillard's security personnel saw the situation escalating as protesters banged on the restaurant's large glass windows and shouted abuse.
'If it had escalated much further, then the safety of the prime minister couldn't have been assured,' he said.
The AFP is conducting an inquiry into the protest and its report is could be completed as soon as next week.
Prime ministerial staff Tony Hodges resigned over the incident after admitting he had spoken to Unions ACT official Kim Sattler and told her Mr Abbott was at the restaurant.
That information was relayed to tent embassy organisers who incorrectly believed Mr Abbott had earlier that day called for the tent embassy to be moved on.
Opposition Attorney General spokesman George Brandis said no one could have known the crowd would be stirred up as it was.
'I don't think anybody could have anticipated the idiocy that caused this crowd to become dangerous,' he said.
Mr Negus said AFP officers had interviewed Mr Hodges, Ms Sattler, tent embassy elders and staff members from the offices of the prime minister and opposition leader.
He said AFP had reached no conclusion as to whether Mr Hodges had committed any offence.
'The investigation is ongoing and it is very difficult for me to say anything further about what may have been said or what a potential outcome may be,' he said.
