underworld figures wanted to help police stop Melbourne's gangland war but remained silent because they were so scared of killer Carl Williams.
They came forward very soon after Williams was arrested and provided vital information to Victoria Police's Purana taskforce.
Det-Insp Gavan Ryan, who this week handed over leadership of the elite taskforce to Det-Insp Bernie Edwards, said the arrest of Williams was a turning point.
"We knew if we could get Williams behind bars that it would make life difficult for him and his friends," Det-Insp Ryan said.
"Certainly the shooting side of things slowed down when we locked him up. Locking Williams up also gave us an opportunity to talk to people who would not talk to us while he was out in the community.
"We always knew if we could pop Williams in the bin we would have a good chance of getting a lot of information, and that's exactly what happened."
It was the arrest of Williams's hitman Sean Sonnet during a failed 2004 attempt to execute Calabrian mafia money man Mario Condello that led to Purana nabbing Williams. Det-Insp Ryan said Purana had gathered enough evidence to implicate Williams in several murders by the time Sonnet was arrested.
"I rang Purana officer Shane O'Connell immediately after Sonnet's arrest and simply said 'Go and get Fat Boy', and five minutes later he rang back to say he had picked up Williams," he said. "We questioned Williams that day, and he ended up getting jailed for 35 years." Williams pleaded guilty to three murders and was found guilty of a fourth. He's a suspect in several others.
Purana was formed in May 2003 to combat the alarming level of gangland slaughter in Melbourne. In the five years since it has charged 58 offenders with 298 offences after bugging more than 500,000 telephone conversations, taping 53,000 hours of conversations and conducting 22,000 hours of physical surveillance.
Purana was so successful at ending the underworld war that Victoria Police decided to make it a permanent taskforce. Its brief is to investigate established and emerging criminal networks. Det-Insp Edwards this week started as the new head of the permanent Purana taskforce. He brings a wealth of experience. He has been in the homicide squad and detective training school, and at busy stations such as St Kilda and Dandenong, since graduating from the Victoria Police academy in 1980.
"Purana has always been headed by people who are very well respected within Victoria Police. They will be a hard act to follow," Det-Insp Edwards said.
"The pressure is on me -- and Purana -- to keep performing."
Det-Insp Ryan said the keys to Purana's success in the gangland war were the resources support it was given by Chief Commissioner Christine Nixon and Deputy Commissioner Simon Overland.
"Christine and Simon got a terrible caning in the media and elsewhere in the early days of Purana, when it appeared to some that things were not happening quickly enough," he said.
"They backed us, provided us with the resources we needed.
"Having that support was a key to Purana's success. It meant we could make big decisions immediately, expensive decisions, knowing force command was behind us.
"Christine and Simon deserve to get all the subsequent plaudits for Purana's success because they took a lot of the criticism before the arrests started happening."
Det-Insp Ryan said while he couldn't say there would be no more underworld killings, he was confident the spate that Purana was formed to investigate had ended.
"Crooks will always kill crooks. It's like prostitution -- you will never take that away," he said.
"But the nature of that particular war is over."