The trouble was no one had done it before and they were flying blind into a blizzard of problems. "One of the bosses had just read Donnie Brasco [the story of FBI undercover agent Joseph Pistone who spent six years infiltrating two New York crime families] and decided we should do the same," says Steve. There were substantial differences between the two investigations. Pistone was of Sicilian heritage and spoke fluent Italian. Steve worked in Sunshine and occasionally ordered Italian sausage on his takeaway pizza. He hadn't expected to work undercover, indeed he hadn't even thought of being a policeman until a year 11 school career day planted the seed. He turned out to be a natural, dux of his Police Academy class and excelling at busy western suburban stations while learning the trade.

When he met his Bendigo-based future wife he transferred to Kyneton where he developed an interest in antiques, a hobby big in the area but rarely associated with burly coppers. It would be a skill he would incorporate in his undercover stint, but more of that later. Transferred to the vice squad he was used to infiltrate gay bath-houses allegedly employing under-age male prostitutes. His cover was decidedly flimsy as he wandered about naked except for a small towel trying to gather evidence. After two years as a Sunshine detective he moved to the prestigious NCA to work on national organised crime targets. He was seen as a rising star – with one officer describing him as "energetic, reliable, competent, trustworthy and loyal". He had a big future – until he went undercover.

It was 1989 when he volunteered with another Victorian detective to take on the dangerous deep intelligence operation. It was at a time when the Mildura Mafia was emerging as a major crime group, dominating marijuana production, buying into local businesses and establishing an Australia-wide money-laundering network. It was hardly a secret with local grape growers managing to become property moguls, restaurant owners and nightclub proprietors, while others struggled to make a living. The Mildura antique shop used in a police undercover investigation into the local Mafia. One such fellow built a 100-square home and owned a couple of Mercedes. Not bad for a self-made battler aged 31.

Steve says a massive hail storm in the 1970s that ruined local crops helped turn many growers towards the lucrative cannabis market. "There was a local saying, 'Why grow zucchinis for $7 a box when you can get $7000 for Italian wheat?' " It may have remained a dirty little local secret if not for the death of a little known insurance broker – Giuseppe Arena – murdered in 1988. The father of three was blasted from behind while taking out the rubbish at his Bayswater home – a classic Italian organised-crime hit that remains unsolved. Known as the Friendly Godfather, he was mooted as the successor to the undisputed head of the Italian Honoured Society, Liborio Benvenuto, who had died six weeks earlier. When homicide detectives investigated Arena's financial status they found he was a prodigious money launderer for at least one Mildura crime family. And so the NCA planned to turn Steve into its own Donnie Brasco. In one way it was a real life experiment with Steve and his mate Chris: human guinea pigs.

"Don't get me wrong, I wanted to do it. We thought it would be a real adventure," Steve says. "But we didn't know what we were doing. We were the test case." Giuseppe Arena, known as the Friendly Godfather, was murdered in an execution-style killing in 1988. In Melbourne Steve was a married policeman with a young son. But in Mildura he was an out of town playboy, intent on making friends and enjoying the good life. The 14-month mission ultimately put an intolerable strain on his marriage that led to divorce. The two police set up an antique shop in one of Mildura's main streets. It was a great cover as Steve could come and go on so-called buying trips while Chris, already handy on the tools, masqueraded as the furniture restorer. Steve says the cover worked so well "we sold furniture to some of the crooks' wives".

As antique dealers with no children who lived together the rumours soon started that they were a same-sex couple. That stopped when Steve hit the clubs, chatting up local ladies and letting it be known he was supplementing his antique income with a side line in drugs. To help set up a cover story he "spotted" an advert for a BMW in The Age and made a production of buying the car for cash. Sure enough one of his targets went with him and saw the transaction through. It was a set-up – police had placed the ad in the paper. This reporter unwittingly put a scare through the camp when we went to Mildura to sniff around the same crooks. "We thought you'd been tipped off about us so we had to lay low for a while." Undercover policing is based on the art of betrayal. You lie, you cheat and you pretend to be someone's friend to gain trust. It is a perfectly legitimate tactic but comes at a cost because the trouble is some crooks are likeable. They love their mothers and their children, they can be generous and funny, which became Steve's trap.

He started to like some of them. "We went on holidays together, I went to their homes – their mothers made me home-cooked meals," he says. Living the life of a party boy he eventually formed a serious relationship with a woman whose parents were local farmers of Italian descent. After his first marriage fell apart they married and had two children. That relationship formed on a lie also collapsed. Steve and Chris lived this double life for more than a year, gathering material on the main crooks in the town. Once they followed a target on country roads in the middle of the night at speeds of up to 160km/h with the lights off. The unmarked police car was driven by an SOG member wearing night vision goggles. "Now that was scary," says Steve. They were pulled out when the bosses feared their cover had been blown after their house was burgled and car stolen and burned out. "The job just turned sour. We still don't know if they cottoned on to us." They shut the antique store and disappeared. Later police raided the property of the man with the 100-square home and found marijuana growing between the vines. Eventually they seized the house as an asset of crime. His brother was ruined by a massive back tax bill.

There are plenty of police who have liked particular crooks but there is no moral dilemma. If the crook is caught committing a crime he is locked up. The undercover has to battle a sense he is not so much working as a police officer but as a professional snitch, gathering information under a cloak of friendship. There are stories around the world of undercovers going rogue, swapping sides and starting to run with the crims. While some are natural actors, capable of taking on a role as if on the stage, others invest so heavily they struggle to return to normal policing. They miss the independence, the adrenaline and the action and find routine station policing oppressive. Undercovers have to be virtually reprogrammed to return to uniform. Johnny Depp in the film Donnie Brasco. In one way Steve simply forgot how to be a policeman and there was no one who could help him back. He says the job changed his personality. "I am more manipulative and calculating than I once was."

The once dedicated policeman drifted until he eventually resigned, "I just couldn't be a copper any more". "I have no doubt if I hadn't done that job I would still be a policeman. It was the worse thing I ever did." In 1991 he, Chris and their controller were awarded the prestigious Chief Commissioner's Certificate for performing an "extremely long, dangerous and arduous undercover operation … It was the first of its kind to be conducted by any law enforcement agency in Australia … The pressure was extreme and the danger continual … The standards displayed by these three sergeants epitomise that which is best in policing." At the presentation ceremony a senior policeman approached Steve's parents and apologised for not doing more for his long-term welfare. His mother replied, "All we wanted is for you to give us back the same son we gave you."