Australia needs to publicly talk tactics on terrorism approaches to free police from fears of undue criticism, a British counter-terrorism expert has told an inquest. 

Deputy Chief Constable Simon Chesterman, head of the British team reviewing the response to the Lindt siege, said the "harsh reality" was terrorist sieges always carried a risk of death. 

Police did not approve a "deliberate action" plan to take the gunman Man Haron Monis by surprise. They entered only after he killed cafe manager Tori Johnson at 2.13am on December 16, 2014. 

Mr Chesterman told the inquest on Friday he would have preferred NSW tactical assault teams to have gone in earlier.

But he said: "Police are 'damned if you do, damned if you don't'."

If police officers "play it long" by waiting and then an emergency forces them to go in, "you're going to be criticised". The same would be true if officers entered before some imminent risk arose and then a hostage was injured or killed.

Coroner Michael Barnes asked about a potential "structural bias" among police towards waiting. He observed that once someone was killed, police in effect "had no choice" but to enter; their hands would be forced.

"Does that set up a bias in an organisation to adopt the second, the 'long' strategy, even though that places hostages and operators at more risk?" he asked.

Mr Chesterman said that was a "critical issue".

"Human nature is you're going to be clouded by justification afterwards and how this is going to play out," he said. But if police did adopt a strategy based on reputational risk, that would be "unacceptable".

Mr Chesterman called for Australia to publicly weigh the risks and benefits of various types of intervention. 

"[The public] need to support police in these issues because police need to be able to make decisions based on minimising risk to the hostages, not minimising risk to the organisations. 

 Siege specialist Inspector Nigel Kefford, another member of the British review team, said the eventual operation to free the hostages was clumsy in parts but "a reasonable job in all the circumstances".

Mr Kefford said police deployed double the number of flash-bang distractors they required. But he said the 22 rounds two officers fired between them was not excessive. 

"It's not like the movies," Mr Kefford said, explaining people are not blown off their feet by shots. He said police are trained to keep firing even as an offender drops, in case they are adopting a new position.

The inquest will hear next week from Police Commissioner Andrew Scipione and Deputy Commissioner Catherine Burn.