But a senior police negotiator involved in the Lindt Café siege that Monis orchestrated in 2014 has conceded he underestimated the threat posed by the gunman that day.

"Thinking back now, yes," the negotiator told an inquest into the Martin Place siege on Friday.

The police negotiator, identified only as "Reg", has given evidence about a litany of issues that appears to have hampered the negotiation team's response to the fatal siege on December 15 and 16, 2014.

The negotiators were ill-equipped and disadvantaged early on as a negotiation truck, used primarily for major incidents, was "unavailable and unusable".

Reg, who was a negotiation team leader and unit coordinator, told the inquest the purpose-built truck had been damaged by weather in 2011 and hadn't been fixed as of December, 2014.

"What would have made it better is if we had our negotiation truck," he said.

"On major jobs we have a negotiation truck that was provided federally to each state and our truck wasn't available on that day.

"It was damaged. It wasn't useable."

The truck was built to be used as a negotiators cell, with whiteboards on the walls, a sound proof section and ability to set up a direct phone line.

The commander of the negotiation unit put in a report in November, 2011, trying to get the truck back, the inquest heard.

Such a vehicle still isn't available today, having been sold-off, Reg confirmed.

Instead Reg's negotiation team of up to five people was crammed into the gaming manager's officer at the NSW Leagues Club, where police were stationed as the siege unfolded.

The phone number of the office was provided to the hostages but it would divert to somewhere else in the club if a negotiator was on the phone.

On one occasion a call believed to be from a hostage was answered by an officer in another part of the building.

The negotiation team also had only one mobile phone between them.

Pressed on how the phone issue inside the leagues club could have been handled, Reg said: "I don't believe there was anything that could've been done with it."

Counsel assisting the coroner Jason Downing put it to Reg that one solution would have been using the mobile for outgoing calls so the landline was free for hostage calls.

"It makes sense, yes," Reg replied.

The inquest also heard how 12 groupings of calls between when the siege began at 9.30am and 1.16pm weren't recorded on a police dictaphone and subsequently hadn't been transcribed.

"As to why things are missing I can't answer that," Reg said.

He agreed it could have been because the recording button wasn't pressed properly or some recordings were taped over.

Under questioning from Peggy Dwyer SC, counsel for cafe manager Tori Johnson's family, Reg was questioned about Monis' behaviour towards the hostages, including allowing them to go to the bathroom on their own and make food.

Reg agreed he thought Monis was less likely to harm the hostages.

Ms Dwyer asked Reg if, considering Monis had a gun, a suspected bomb in his bag and a violent history, he underestimated the gunman's dangerousness.

"Thinking back now yes…" Reg replied.

After police positively identified Monis, a psychiatric profile was done and handed to Reg, who was a conduit between his superior, the negotiation unit commander, and his team of negotiators.

Reg said he might have glanced at it, but didn't read it, and passed it on to another negotiator to peruse.

In the siege's final moments, Mr Johnson was executed by Monis before police stormed in. Barrister Katrina Dawson died after she was hit by a ricochet police bullet fragment.

The inquest continues.