More tough questions to be asked of cops at Lindt cafe inquest

Senior police involved in Sydney's Lindt cafe siege are set to face more tough questions when a coronial inquest resumes on Monday.

Police management of the siege has been thrust under the microscope, with a senior negotiator the last to take the witness box at the inquest.

He admitted to underestimating gunman Man Haron Monis, and spelled out a litany of flaws in his crew's equipment.

It has been revealed that hours of transcripts and recordings of hostage calls during the December 2014 siege are missing, and could have been taped over or never recorded in the first place.

A specialist negotiations truck wasn't available on the day - it had been badly damaged three years earlier and still hasn't been replaced.

Negotiators instead worked from a cramped room with one fixed line phone, no whiteboards and no live feed of the siege.

The inquest has heard when the phone was in use, at least one hostage call was diverted elsewhere in the police forward command centre, and the senior negotiator didn't think to tell his team to make calls on their mobiles and keep the landline free.

The commander in charge of the siege, Assistant Commissioner Mark Jenkins, has also faced questions about information missed, opportunities overlooked and messages not relayed up the chain.

Officers ultimately stormed the cafe shortly after 2am on December 16, 2014, after Monis executed cafe manager Tori Johnson.

Monis was killed and barrister Katrina Dawson also died when she was hit by a police bullet.