Former Victoria Police chief Christine Nixon knew in 2005 that lawyer Nicola Gobbo was a police informer, her successor Simon Overland now claims.
Last year Mr Overland told a royal commission he couldn't remember if he told his former boss the gangland lawyer was also a police informer, but the resurfacing of his former work diaries has helped his memory, he says.
Three of Mr Overland's police diaries were discovered in a Melbourne storage facility late last year, days after he claimed he never kept any.
After reading diary entries over the inquiry's summer break, Mr Overland returned the witness box on Tuesday with changes to his evidence.
"Having now reviewed my diary, I note that I was involved in 14 meetings with Ms Nixon regarding Purana Task Force matters and I believe that I did, in fact, inform her of Ms Gobbo's recruitment on 29 September 2005," he said.
"I have no independent recollection of this meeting, but note the contents of my diary entry that indicates I did tell her about the registration of Ms Gobbo as a human source."
But Ms Nixon claimed in her own evidence last year that the first she believed she knew about Ms Gobbo - known as Lawyer X - being a police informer was when she was publicly identified.
Mr Overland in a new statement to the inquiry on Tuesday was adamant he made Ms Gobbo's registration known to Ms Nixon soon after he learned of it himself.
But his certainty wavered in the witness box.
He said he now believes he did tell Ms Nixon, but followed up by saying he "probably did" tell her that Ms Gobbo was the human source known as 3838.
"I don't know whether I specifically told her," he added.
It's not clear if Ms Nixon will be recalled to respond to the claims.
Mr Overland's newly-discovered diaries cover a period from February 2003 to May 2008. There's a gap from October 2006 to November 2007 which has prompted Mr Overland to concede a fourth diary may exist.
The diaries were found in a police archive facility after a tip from Mr Overland's former chief of staff.
Mr Overland apologised for not remembering the diaries existed, claiming he was "convinced they didn't exist".
He also used his return to deny allegations made during the inquiry, including accusations of "self-serving secrecy".
"Any suggestion that my conduct at Victoria Police ... was corrupt, perverted the course of justice, was dishonest or facilitated any dishonesty in the court system, or sought to cover up the use of Ms Gobbo is completely denied by me and does not accord with my conduct as reflected in my contemporaneous diary notes," he said.
Australian Associated Press