Mum of slain Lindt Cafe hostage storms from inquest

The mother of slain Lindt cafe manager Tori Johnson has called a police commander "an absolute disgrace" before storming out of the inquest where he was giving evidence.

The forward commander in charge when officers stormed the cafe, who can't be named, described the Sydney siege as "high stakes games", prompting the lawyer for the Johnson family, Gabrielle Bashir, to ask if he wanted to apologise.

"It was not a game on the night," Ms Bashir said of the December 2014 siege which ended with the deaths of Mr Johnson, gunman Man Haron Monis and Katrina Dawson.

The officer did not apologise but said he accepted that "game" was not the best word to have used.

During the brief exchange Mr Johnson's mother Rosie Connellan and father Ken Johnson collected their things and marched through the almost-empty public gallery towards the hearing room's exit.

Ms Connellan paused at the door and told the officer "You are an absolute disgrace," before hurrying out.

Earlier on Tuesday, the inquest heard the siege was a terrorist attack but elements of it differed from how ISIS-inspired violence had played out overseas.

The commander made the comment as he was questioned whether early intervention by police would have maximised the chances of hostages surviving.

"In ISIS inspired sieges the maximum chance of survival of the hostages is through early intervention by police," the inquest heard from a report by UK terror experts.

But the forward commander maintained that "time was his friend" during his second day giving evidence, telling the inquest that ISIS attacks were more violent than events in the Lindt cafe.

"They commence with a high level of violence, high levels of death, whether by a person-borne bomb or automatic gun fire, they are not a siege situation," the detective chief superintendent with 35 years' experience said.

Because of these differences, storming the cafe to end the siege was not the best strategy and police persisted with their contain-and-negotiate approach, he added.

The inquest continues before NSW coroner Michael Barnes.