Overland insists he wasn't made aware Gobbo was giving up client information

Former Victoria Police chief commissioner Simon Overland has told the royal commission investigating the use of Lawyer X, Nicola Gobbo, as a police informer that he was not made aware the gangland barrister was giving up information on her clients.

The battle lines between Victoria Police command and lower-rung police that managed Ms Gobbo were drawn from the start of the royal commission investigating the force's use of the lawyer.

For police commissioner Simon Overland arrives at the royal commission on Monday.Credit: Jason South

But the gap between them widened further with Mr Overland taking the stand on Monday. Sacked last week as Whittlesea council chief executive, a relaxed Mr Overland opened his evidence by telling the inquiry he was "pleased to be here today" to answer questions.

Mr Overland has been painted as the police officer who drove Ms Gobbo's use as registered informer 3838, whose role may now lead to some of the state’s most high-profile convictions being overturned.

Though he told the inquiry that he knew from the start the precarious nature of using a lawyer as a police source, experienced investigators never told him she was informing on criminals she was acting for.

“At no time was I made aware of the fact that Ms Gobbo was either breaching legal professional privilege or acting for people against whom she was informing,” he said.

“Had I been aware I'd have taken action."

Mr Overland said it was his understanding Ms Gobbo was registered in 2005 because her life was at serious risk from drug boss Tony Mokbel.

He said she had crossed professional boundaries and had become a facilitator of criminal conduct.

Mr Overland said she couldn’t walk away.

“She was ideally placed to pass information on,” he said.

"[People like her] are important to the operation of the syndicate and they tend to have really crucial information about the people who sit at the heart of those syndicates.

"They simply can't walk away, it's a death sentence to try and do so."

Though Mr Overland said he didn’t know Ms Gobbo was giving information about her clients, the commission has previously heard she was recruited to bring down Mokbel’s syndicate after having acted for him as his lawyer from 2002.

Mr Overland joined Victoria Police from the Australian Federal Police from 2003 as the assistant commissioner in charge of crime command.

He became a deputy commissioner in 2006 before succeeding Christine Nixon as chief commissioner in 2009.

He told the inquiry he could not recall telling Ms Nixon that Ms Gobbo was a human source.