For much of the first half of the nineteenth century, the burgeoning colony of Van Diemen's Land was driven by the assignment system, which saw convicts delegated to free settlers to provide them with free labour.

However, come 1839, assignment was replaced by the probation system.

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Michael Sprod, the proprietor of antiquarian bookstore Astrolabe Booksellers in Hobart, was a contributor to the Companion to Tasmanian History website. He has written that the key principle of the probation system was that punishment and reform could be achieved through a mix of labour, religious instruction and education.

Under the system, convicts without a life sentence were confined for a period before undertaking labour in gangs at the various probation stations throughout the colony.

The convicts' progress was marked and, if their behaviour was satisfactory, they were given a probation pass, which made it possible for free settlers to hire their labour. Meanwhile, those with passes who were still waiting for employment stayed at the stations, contributing to public works.

The probation station at Westbury was established in 1842, operating as a hiring depot. It was able to accommodate roughly 400 convict pass-holders.

Located on Franklin Street, bordered by what's now the Meander Valley Highway and Lyall Street, the site of the probation station is now a residential area, where the Westbury Sports Centre and Recreation Ground is situated.

In 1847, colonial administrator Charles La Trobe, after whom La Trobe Street and La Trobe University in Melbourne are named, was appointed interim administrator of Van Diemen's Land.

He was brought in after the dismissal of Lieutenant-Governor John Eardley-Wilmot, whose downfall was attributed to the perceived failure of the probation system.

La Trobe completed a report on the system in his time as interim administrator of the colony.

He summed up the system thus:

"I need not conceal my conviction, that any system that would accumulate vice without a sure and corresponding power to restrain and reform, must be termed a vicious one, and that the Probation system, so called, has been a fatal experiment as far as it has proceeded, and the sooner it is put an end to the better, for the credit of the Nation and of humanity."

The La Trobe report was handed down in 1847, the same year the Westbury probation station closed. It led to a number of modifications of the probation system over the years, until it was completely brought to an end in 1853, when the transportation of convicts to Van Diemen's Land was abolished.

La Trobe found that the station in Westbury, constructed of wood, was "very slight".

Amanda Taylor, of the Westbury Historical Society, said there were up to 334 convicts at the station, mostly employed in agriculture. While some resided there, others boarded with free settlers who utilised their labour.

"[La Trobe] noted that the superintendent had a comfortable cottage, but that the quarters for the other officers were very inferior," Ms Taylor said.

"With respect to the remainder of the probation station, the general state of the establishment at the time it was inspected calls for no particular remark."

In physical terms, the Westbury Probation Station has been lost to history, with none of its above-ground structures having survived.

"It's believed that the destruction of the buildings began almost immediately after the probation station closed, with the opening of Franklin Street in August 1848," Ms Taylor said.

"It's also unlikely that any subsurface features remain, as there's been significant development in the area."

The memory of the place, though, lives on.

Various detritus has been collected from the site, including old crockery and nails.

And now, more than 170 years after it was razed to the ground, the old probation station at Westbury is relevant again.

With the proposal to build a Northern prison at the Valley Central Industrial Precinct site just north of the town, the state government will be hoping that history doesn't repeat itself.

Because the last time convicts were at Westbury, a politician's career was destroyed.