A decorated police officer who was once a deputy commissioner at Victoria Police says he suspects corruption and conspiracy were at play when gangland boss Carl Williams was murdered in prison.

Sir Ken Jones told Neil Mitchell it was “all too convenient” for Williams to be killed in a maximum security prison in 2010.

Williams had been co-operating with Victoria Police over unsolved murders at the time of his death.

Fellow inmate Matthew Johnson was convicted of the murder.

Sir Ken, who led the initial investigation on the Williams murder, said he was of the opinion there were likely other forces at play.

“For me, there are a lot of questions that remain unanswered,” he said.

Press PLAY below to hear the questions he says need answering

Photo: 9 News