The 39-year-old underworld bo' />

Were corrupt police officers behind the prison slaying of Melbourne crime lord Carl Williams, whose murderous reign was brought into our living rooms by the Underbelly drama series?

Carl Williams should have been as safe inside Barwon Prison's Acacia unit as the people of Melbourne were from him.

The 39-year-old underworld boss was held in a modern maximum security wing in one of Australia's most secure jails, sitting off Bacchus Marsh Rd on open, flat country near the port city of Geelong.

Other notorious criminals have survived there.

Gangland lawyer Mario Condello, charged with conspiring to murder Williams, died only when he was released on bail to stand trial.

Others remain alive behind Barwon's walls: Julian Knight, who killed seven and injured 19 in the 1987 Hoddle street massacre; serial killer Paul Denyer; drug trafficker and Williams' associate Tony Mockbel; and Francesco Mangione, who killed a cousin in a Mister Whippy turf war.

But on Monday, as Williams sat reading a newspaper in a common room with two trusted inmates, he was bludgeoned to death with an exercise bike bar.

Few will mourn his passing. Williams was a vicious thug who dealt in drugs and death as a prominent member of Melbourne's underworld.

He triggered the decade-long gangland wars that killed as many as 30 victims by revenge attacks on the rival Moran clan after he was shot in the stomach during a dispute over the amphetamines trade.

The carnage of the war was often brutally public. Jason Moran, scion of the long-established crime family, was shot dead with associate Barbaro Pasquale in front of five children.

His father Lewis was gunned down in a Brunswick club. Others were killed in a supermarket carpark, in busy city streets, and outside shops and restaurants.

Williams was known to have been responsible for the deaths of at least 10 rivals. He pleaded guilty to four, and to conspiring to murder another, in a deal that put him behind bars for a minimum 35 years but gave him some hope of dying a free man.

Between them, Williams and his enemies virtually wiped each other out. Infamous former gangster Mark "Chopper" Read noted on Adelaide radio: "There's only me and (underworld identity) Mick Gatto left."

But the Acacia Unit murder has opened an entire new set of wounds for Melbourne. Even if police believe renewed killings are unlikely to erupt among the survivors, the wars have left a vacuum that others will fight to fill.

And in a city too often rocked in the past by corruption, the nature of Williams' death and possible links to bent police are too obvious to ignore.

The politics of the investigation are also volatile and potentially dangerous for a State Government that has for years resisted the creation of a dedicated anti-corruption body and which is so far refusing calls for a royal commission into Williams' murder.

Regardless of the deaths of so many underworld figures, organised crime remains embedded in Melbourne. Its existence has been confirmed by a series of commissions and inquiries - both local and national - and by the Australian Crime Commission, which estimates its Australia-wide income at least A$10 billion ($12.5 billion) a year.

The Calbrian 'Ndrangheta (Honoured Society) has been established since the 1920s and in the 1960s sparked a turf war in Melbourne's Victoria markets. United States Narcotics Bureau Italian crime expert John Cusak was imported to investigate, but his confirmation of 'Ndrangheta's presence, and his warnings of far more sophisticated operations to come, were largely ignored.

Alleged 'Ndrangheta associates were involved in the crimes and wars that surrounded Williams and the Moran family, which had grown from Irish thugs who controlled the waterfront through the now-defunct Painters and Dockers Union.

There was also the Carlton crew, a mafia-style gang whose members included Condello, Alphonse Gangitano and brothers Gerardo and Vince Menalla - all killed - and the Sunshine crew led until his murder by hitman Andrew "Benji" Veniamin.

With other players such as Bulgarian-born Nikolai "The Russian" Radev, the profits were so huge and the doors so wide that corruption became inevitable.

"The very nature of the job exposes a police officer to the temptations of corruption," the Victorian Office of Police Integrity said in a recent report.

"Some have been tempted to cross the line of legality to gratify some private desire, greed or vice."

A task force set up to investigate corruption connected with organised crime a decade ago saw five members of the Melbourne drug squad jailed for up to 12 years on trafficking and other charges.

Two years ago secret police surveillance reports turned up in the hands of suspects. And the release of an OPI report on associations compromising police awaits the conclusion of court proceedings.

Williams' murder has rubbed already raw nerves. The fact is that he was beaten and left to die by another inmate without being noticed in a maximum security unit.

One of the men removed the seat support from an exercise cycle, bashed Williams repeatedly on the back of the head, then dragged him back to his cell.

CCTV footage showed the murder clearly, and should have been seen immediately on the guards' screens. But the closest, in a room just 10m away, was reportedly using the telephone as Williams was attacked and left to die of his injuries and cardiac arrest.

It was not until the other prisoner, Thomas "Little Tommy" Ivanovic, advised the guard to check on Williams 25 minutes later that the murder was discovered.

There appears to have been no animosity beforehand, and prison officials say Williams had been happy to spend his time out of solitary with his alleged killer - whose name has been withheld for legal reasons - and another inmate.

It is possible that he died because of some reason related only to his confinement.

The Melbourne Age reported that the alleged killer is an enforcer of a gang called Prisoners of War, an apparently white supremacist group that has terrorised other prisoners for three decades.

Or he could have been killed for other reasons. Police are investigating alleged links between Ivanovic, a convicted killer, and allegedly corrupt police.

Ivanovic is being called as a prosecution witness against former drug squad detective Paul Dale, accused of murdering informer Terrence Hodson, who provided evidence against Dale and another officer related to the theft of drugs worth A$1.3 million ($1.6 million).

There is speculation that Williams had turned informer and may have been killed to disrupt other prosecutions. The suggestion is that prison officers may have been paid to turn a blind eye.

His lawyer, Rob Stary, who is demanding a royal commission into the murder, said Williams was a "goldmine of information" whose death would jeopardise a number of sensitive investigations.

On the day Williams was murdered a newspaper revealed that police were paying private school fees for his daughter Dhakota.

Victorian Police Deputy Commissioner Sir Ken Jones conceded that some investigations could now be at risk, telling a media conference: "It doesn't take a genius to work out that there will be ramifications and impacts and we are alive to that.

"As we speak I've got people working on those."

There are now five inquiries into Williams' death: an OPI review, an Office of Corrections inquiry that will specifically include the possibility of corruption, a coronial inquiry, and investigations by the homicide squad and a special police Task Force Driver.

The task force will be led by Superintendent Doug Fryer - who headed the probe into drug squad corruption - with instructions from Sir Ken to "leave no stone unturned".

But Williams' killing and its implications, and the long history of corruption within the state, have failed to convince Premier John Brumby of the need for either a royal commission or a permanent corruption-busting body in the state.

Victoria and South Australia are the only two states without such a body, and Labor has for years refused to concede the need. Brumby points to the OPI, rejecting criticism that its powers and functions are not adequate.

Under pressure, he last year established a review of the state's integrity bodies led by Elizabeth Proust, former secretary of the Department of Premier and Cabinet, but this week made no commitment to any possible call for an independent anti-corruption watchdog.

"She may recommend going in that direction or she may not," he said. "I don't rule in or rule out any of the recommendations she might make. We'll look at them objectively."

But Brumby has dismissed a royal commission as a waste of time and money, saying though Williams' murder was "obviously unacceptable" the victim had been a serial killer: "If I had the choice of putting tens of millions of dollars into (an anti-corruption body) or putting it into hospitals, or bushfires, or more police, I'd choose the latter."

For a state now waiting to learn if it remains riddled with corruption, and who will fill the vacuum left by the wholesale slaughter of Melbourne's crime lords, that might not be enough.

VANISHING ACT: How Melbourne's Mr Bigs disappeared
Lewis Moran
62, clan patriarch, father of Jason and stepfather of Mark, shot dead at a Brunswick club in March 2004.

Jason Moran
35, career criminal whose shooting of Carl Williams launched the wars, gunned down with associate Pasquale Barbaro in June 2003.

Mark Moran
35, killed June, 2000,

Alphonse Gangitano
40, shot dead in the laundry of his Templestowe home, January 1998. Head of the Carlton Crew.

Graham The Munster Kinniburgh
62, long-time underworld heavy and Carlton Crew associate, shot at home in Kew in December 2003,

Carl Williams
39, drug-dealer and multiple killer, murdered in prison this week,

Andrew Benji Veniamin
Hitman and drug dealer, killed in a Carlton restaurant in March 2004.

Nikolai Nik Redev
43, Bulgarian-born enforcer, extortionist, armed robber allegedly associated with the Russian mafia, shot in Coburg, April 2003.