It is the first time the circumstances of the fire have come to light after the rifle, seized by police in a raid on Tanner's Williamstown home in February this year, was found to have still been registered to a man by the name of Roy Bostock.

The connection between Bostock and Tanner was that Bostock sold his prized property, Preston Estate, to the Tanner family in 1991.

A Fairfax Media investigation has unearthed the peculiar circumstances of a fire that burnt down the shearers' quarters on the property the night before the sale went through.

The shearers' quarters had been a stumbling block during negotiations between Bostock and Tanner, who indicated he had no need for the building and wanted a discount.

The fire subsequently dropped the sale price of the 400-hectare parcel of land by about $30,000.

Not only did Tanner, who was a policeman at Benalla at the time, investigate the fire himself - which raises questions about a conflict of interest - but the cause of the fire was deemed an electrical fault despite electricity not running to the building for 20 years.

It was not the first time Tanner was linked to an impeccably timed fire.

In 1995, two months after the body of transsexual St Kilda sex worker Adele Bailey was found in a nearby mineshaft, his brother Laurie Tanner's Bonnie Doon home burnt down and all traces of potential forensic evidence were wiped.

The same farmhouse was where the body of his sister-in-law Jennifer Tanner was found in 1984 in one of the state's most baffling deaths. Local police first thought, in their bungled investigation, that Jennifer Tanner had died after shooting herself twice in the head.

Through the webbing of each of her hands were bullet holes.

One coronial inquest returned an open finding into her death while another in 1998 named Tanner as her killer.

The circumstances surrounding the Preston Estate fire were buried among the more explosive rumours that dogged Tanner until the police raid on his Williamstown home in February this year.

The raid at Tanner's house comes amid a family feud and after his brother reported legal documents were stolen from his house in Mansfield.

The documents were never found, but police discovered the old British air rifle along with police-issue ammunition and identification.

The air rifle is still registered to Bostock, a five-time shire president and war veteran who died in 1998.

A farmer who managed Bostock's prized Preston Estate in October 1991 still remembers the morning Tanner arrived in his driveway.

"He (Tanner) came down the drive and he said, 'You know the shearers' hut burnt down?' " the farmer, who wanted his identity protected, said.

He said Tanner, then stationed at Benalla, told him there were two potential causes for the fire; that Mansfield youths drinking there burnt it down or an electrical fault sparked the blaze.

Both explanations stretched credulity. The problem was, the farmer said, there hadn't been electricity to the shearers' quarters for about 20 years and youths drinking on a property on farmland 10 kilometres out of town seemed far-fetched.

Fairfax Media understands Tanner eventually concluded the fire was caused by an electrical fault.

A close friend remembered Bostock's reaction clearly.

"He definitely thought it was a wilful act," he said.

Bostock, for whom insurers would later reimburse the $30,000, went ahead with the sale so he could move to another property that had belonged to his forebears on the other side of town.

Bostock sub-divided the estate he ran for 50 years and the prime land is now dotted with hobby farms and a country club that sits on the foreshore to Lake Eildon.

The parcel of Preston that was sold to the Tanner family is still run by brother Laurie Tanner.

At its centrepoint is a big, looming woolshed that obscures any remnants of the shearers' quarters that once stood behind it.

The woolshed holds secrets, too - inside it Laurie Tanner was attacked, stabbed with a boning knife in 1998 by an unknown assailant a month before the second inquest into his wife's death began.

That was the inquest where Coroner Graeme Johnstone found that Tanner had killed his sister-in-law.

Tanner has never been charged for Jennifer Tanner’s death, nor has he been charged for involvement in Adele Bailey's demise. He has always denied any involvement in both cases.

But Tanner, the survivor of two murder investigations, is expected to be charged for the very first time.

His unblemished criminal record could be undone and not by a particularly grave offence, but for firearm charges related to an old gun that belonged to a farmer from whom his family once bought property.