A senior policeman has been questioned during the Sydney siege inquest about whether an email from New South Wales Police Commissioner Andrew Scipione amounted to interference with police operations.

The Lindt cafe inquest is examining the deaths of three people, hostages Katrina Dawson and Tori Johnson, and gunman Man Haron Monis, who were killed during the siege at Sydney's Martin Place in December 2014.

The three most senior police officers in NSW will reveal what operational decisions, if any, they made during the Sydney siege when they give evidence this week.

On Monday, the inquest heard an email was sent to Acting Deputy Commissioner Jeff Loy at 11:50pm on December 15 directing him to remove a YouTube video that had been posted online.

Deputy Commissioner Loy was the conduit between the Police Operations Centre and the State Crisis Centre, after taking over the role from the Deputy Commissioner Catherine Burn about 10:00pm that night.

The inquest earlier heard Monis forced hostages to read messages during the siege and then post them online.

Senior officer did not think Commissioner was 'interfering'

Counsel assisting the coroner Jason Downing read the email Deputy Commissioner Loy received from Commissioner Scipione, less than three hours before police stormed the cafe.

"This was just sent to me, let's move to have it pulled from YouTube ... I'll leave it to you," Deputy Commissioner Loy quoted Commissioner Scipione as writing.

Mark Jenkins raised concerns that the deliberate action plan could risk two or three deaths. ( ABC News: Luke Rosen, file photo )

At the inquest, Deputy Commissioner Loy was asked whether the decision to take down a video was an operational issue that could have consequences for the hostages in the cafe.

He replied: "At the time, I did not make any connection that the Commissioner was interfering [with operations]."

The inquest also heard Deputy Commissioner Loy spoke to the siege operations commander, Assistant Commissioner Mark Jenkins, during a call about 12:30am, less than two hours before police stormed the cafe.

He said Assistant Commissioner Jenkins raised concerns that a deliberate action plan, a pre-emptive operation to storm the cafe, could risk two to three deaths.

Deputy Commissioner Loy said he did not provide any advice but did support the operational commander's view.

"He wanted to continue with the contain and negotiate strategy," Deputy Commissioner Loy said.

Statements released after he finished giving evidence show he thought Assistant Commissioner Jenkins' analysis of the situation was "considered".

The inquest has previously heard that a delay between two tactical police teams storming the Lindt Cafe was one of the elements that caused a "clumsy and messy" end to the siege.

Deputy Commissioner's text messages 'can't be retrieved'

Police are still trying to retrieve text messages sent by Deputy Commissioner Burn during the operation.

The inquest has previously heard the police have not been able to retrieve the text messages because Deputy Commissioner Burn had updated her phone since the siege.

During the siege she was the adviser to the NSW Crisis Policy Committee and media spokesperson.

Andrew Scipione and Catherine Burn are testifying before an inquest into the Sydney siege. ( AAP: Mick Tsikas, David Moir )

The barrister acting for police, Dr Ian Freckelton QC, told the inquest today extra efforts had been made to retrieve messages from her phone but it was "not possible to recover any further texts".

He said efforts were continuing but "these matters will take some time".

On the stand late this afternoon, Deputy Commissioner Burn was not able to answer counsel assisting the inquest Jeremy Gormley's question about the number of texts she sent.

When asked if the texts dealt with the progress of operations, she replied: "I think that would be highly unlikely."

She said she routinely deleted messages and they were along the lines of asking people to call, discussion on briefing times and messages of support to police.

But she did indicate there was a message to Acting Deputy Commissioner Loy about the emergency response.

"If they could be recovered, that would good," she said.

Deputy Commissioner Burn went on to tell the inquest it was not her role to give orders or directions during the operation, and it was important to keep operation decisions at that level.

"I might think I have a great idea but it might be completely wrong or not up to date, it's even dangerous to think you can have these conversations."

She will continue to give evidence and is expected to be face further questions on the nature of the text messages and the extent of her role during the operations.

Police Commissioner Scipione will also give evidence in the next few days.

They were to give evidence a fortnight ago but their appearance was delayed as documents had not been provided to all the legal teams, including those representing the families of Ms Dawson and Mr Johnson.

Outside the inquest, Deputy Commissioner Burn said she welcomed the "opportunity to contribute to this important coronial inquest".

The families of Mr Johnson and Ms Dawson had lobbied for the Commissioner and his deputies to explain their actions on the night.

The parents of Mr Johnson have also previously slammed a senior police commander as an "absolute disgrace" after he described the siege as a "high-stakes game".

NSW coroner Michael Barnes is set to hand down his findings later this year.