Victoria Police have discovered three diaries belonging to Simon Overland at a storage facility in Melbourne's south-west just days after the former police chief told a royal commission he did not keep diaries.

The heat was turned up during Mr Overland's fifth day at the royal commission investigating barrister-turned-police-informer Nicola Gobbo, when a lawyer representing former drug squad detective Paul Dale accused him of "self-serving secrecy" in his "naked ambition to become chief commissioner".

Mr Overland emphatically denied on Monday at the royal commission that he had kept any diaries.

But his former chief-of-staff notified the commission that day that he remembered packing up Mr Overland’s diaries after his boss resigned from the police force in 2011.