And why did that deputy, Catherine Burn, appear to know nothing about the resourcing difficulties facing front-line police negotiators and commanders as they desperately tried to bring the Lindt cafe siege to an end?

There was no mistaking the furious demeanour of counsel assisting the coronial inquest, Jeremy Gormly SC, as he got to his feet on Tuesday morning with the bombshell revelation that a long text message from Commissioner Scipione sent to Ms Burn sometime on the night of the siege had been found in a last-minute scouring of police archives.

Ms Burn had previously told the inquiry she believed she'd deleted text messages from the siege, not considering them significant enough to keep. This one, it seems, had been overlooked by everyone except a sharp-eyed officer from the professional standards command who unearthed it last Monday evening.

It survived because Ms Burn converted it to an email and sent it to herself at 10.37 pm on December 15, 2014, soon after going off duty for the night and then, seemingly, forgetting about it. She professed herself "shocked" at its sudden emergence.

Just why it remained buried until almost the second last day of the the long-running inquiry is a large enough mystery. Even more perplexing is why Ms Burn knew nothing of the technical issues that were plaguing her officers as they tried to monitor an increasingly agitated Man Haron Monis.

A long list of the woes encountered by police on the night was put to her by Phillip Boulton SC, counsel for the family of slain barrister Katrina Dawson.

Was she told about the difficulties the State Technical Investigation Branch (STIB) was having with gaining quality video surveillance of the siege site? No. Was she told of problems with police radios? No. Told of police running out of batteries for radios? No. Or of delays with a listening device? No. Or that when the police first set up their forward command post there were " very rudimentary" phone services available to them? No. So when Mr Scipione sent her the message about the need to boost technical resources for the future, did she know what he was talking about? No, she replied again.

Did she make active inquiries with her commanders to see if their systems were operating properly? "In terms of equipment and resources, I do not have that role," she responded. "If there are resourcing issues it's up to the police commander and police forward commander to rectify it; if they can't, ithey will come to me."

But they didn't. And she, apparently, didn't ask. Ms Burn has overall responsibility for counter-terrorism and special tactical operations.

But that night she "took on a different role" she said, liaising with the State Crisis Policy Committee, which included the premier and state ministers. Yes, her commanders could come to her for advice, but she doesn't recall offering any. She did not visit the forward police command post. And she stressed it was not in accordance with "protocol" that evening to be issuing orders to the commanders in charge of siege management. Yet when it was put to her that "that day was a day for your leadership", she responded "yes". Whether optimal leadership was exercised on the night – by her and others – remains a key question for NSW Coroner Michael Barnes.