Aside from the gold-embossed logo of Victoria Police, the missing diaries could physically resemble thousands of others, available at stationery stores across the state.

But that's where the similarities end.

Key points: Simon Overland is being questioned about his diaries at the Lawyer X royal commission

Simon Overland is being questioned about his diaries at the Lawyer X royal commission Mr Overland's diaries surfaced after he denied ever keeping diaries or day books

Mr Overland's diaries surfaced after he denied ever keeping diaries or day books Mr Overland says diaries indicate he told then-police commissioner Christine Nixon that Nicole Gobbo was a police informer

Inside these electric blue tomes, scrawled in the hand of a former Victoria Police chief commissioner, are dates, details and notes only a handful of people were privy to.

And their re-appearance has sent lawyers at the Royal Commission into the Management of Police Informants scrambling because their existence was disputed by their owner, Simon Overland, until the eleventh hour.

The royal commission is investigating how Victoria Police managed its informants, including criminal barrister Nicola Gobbo, also known as Lawyer X, who both represented and informed on her clients.

The discovery of her conduct has already led to one murder conviction being quashed.

Barrister-turned-informer Nicola Gobbo, photographed in an undisclosed secret location in late 2019. ( ABC News: Greg Nelson )

And the re-emergence of the diaries has today already led to one key contradiction being aired.

Late last year when another former Victoria Police chief commissioner, Christine Nixon, gave evidence, she told the inquiry that she was never told Ms Gobbo was a police informer.

"I don't recall being told she was a human source — ever," Ms Nixon said at the time.

But Mr Overland's missing diaries paint a different picture.

"Having now reviewed my diary, I note that I was involved in 14 meetings with Ms Nixon regarding Purana Taskforce matters and I believe that I did in fact inform her of Ms Gobbo's recruitment on 29 September 2005," his statement said.

"I have no independent recollection of this meeting, but note the contents of my diary entry that I indicate I did tell her about the registration of Ms Gobbo as a human source."

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Overland's diary backflip

While he may have disagreed with Ms Nixon's initial statement about how much she knew, it is only now, with the reappearance of the denied diaries that Mr Overland can point to what he believes is proof that he informed his then-boss.

When he initially took the stand late last year, he told the royal commission he never kept diaries or day books.

Just days later, and on what was meant to be the last day of his testimony, the royal commission was informed that Victoria Police had found Mr Overland's diaries from 2003, 2004 and 2007.

While they held limited and innocuous information, the commission heard they could still be useful.

The diaries indicated Mr Overland was briefed on key issues being faced by Victoria Police's Purana Taskforce during the height of Melbourne's gangland war, including the murder of key identities.

Their discovery caused royal commissioner Margaret McMurdo to recall Mr Overland to be cross-examined about the diaries.

Today, Mr Overland took the stand to tell the inquiry he was "none the wiser" about the existence of the diaries.

"I was convinced they didn't exist," Mr Overland said.

He told the inquiry he remembered keeping a diary during his career but believed he stopped this practice while he was still at the Australian Federal Police.

"I didn't specifically recall restarting in Victoria Police," he said.

In a supplementary statement to the inquiry, Mr Overland apologised for not remembering the existence of the diaries.

But he used his testimony today to downplay the missing diaries.

"I don't think they're of much value to be honest," he said, telling the inquiry that more comprehensive records were kept electronically.

Mr Overland used the witness box today to remind the inquiry that he was concerned about the use of Ms Gobbo "from the outset".

"I thought because of the threats that were against her from Tony Mokbel … the best of a bad set of options was to use her as a human source with the hope to dismantle the Mokbel syndicate, remove the threat and then manage her out of the organisation," he said.

"That was my hope at the outset and my view was that if this was to all end happily, that was probably the only way that that could or would occur."