AT THE height of the Tasmanian pulp mill protest, Bob McMahon's phone would start ringing at 6am and wouldn't stop until midnight. McMahon was the go-to man everyone would call about the $2.3 billion project at Bell Bay first proposed in 2004 by the giant timber company, Gunns.

Back then, the project was hailed by federal government, with then prime minister John Howard pledging to throw in $5 million as a pre-election sweetener. Opposition leader Mark Latham also backed the mill as a big plus for the island state's environment and economy. The Tasmanian government welcomed it, as did the Chamber of Commerce, but McMahon's small band of protesters - under the banner of TAP (Tasmanians Against the Pulp mill) - would not go away and their campaign became one of the longest and most divisive in Australian history.

McMahon's wife, Susie, says her husband became the voice of the protest movement because he could ''think on his feet''. She recalls the media would often ring early in the morning and McMahon would ''get straight out of bed, open his eyes and give a quote that made sense''.

Their Launceston home became TAP campaign headquarters and month after month, year after year, the couple became a contact point for the community. McMahon, a rock-climbing instructor, grew from a crowd-shy outdoors bloke, a former kid with a stutter, to a leader who addressed hundreds of rallies and meetings so effectively that the 137-year-old Gunns company, also plagued by dropping pulp prices and the high Australian dollar, eventually buckled.

''We held river rallies with big flotillas of boats,'' he says. ''We had up to 15,000 people protest in the streets of Launceston. We turned the West Tamar Council and the Launceston City Council against the mill by sheer public pressure.

''To this day no one can work out how we were so far ahead of Gunns but we would get many anonymous phone calls with information. A typical call would be something like: 'I can't tell you how I found this out, Bob, but …' then they would pass something on and hang up.''

On Tuesday, eight years after the mill was first proposed, the once-mighty Gunns went into administration, $900 million in debt. The McMahons' phone rang again with calls from media and supporters. Finally, it seemed, Goliath had fallen and the Bell Bay pulp mill - like an earlier pulp mill proposed by a foreign conglomerate at Tasmania's Wesley Vale in the 1980s - was dead.

Whether this would have happened if McMahon had not led the charge is a moot point - but the strange fact is that his transformation to unlikely crusader came about thanks to a random seat allocation on a plane flight in Chile in January 2005.

McMahon had been heading south out of Santiago on holiday, intent on sailing and rock-climbing, but happened to notice a report in the newspaper being read by the man in the next seat. The report concerned widespread pollution caused by a new pulp mill in the wetlands at Valdivia in southern Chile, an environmental scandal in which both wildlife and plant life had been wiped out. According to the report there were public calls for the mill to be shut down.

It turned out McMahon's fellow passenger was an architect with the firm involved in the mill's design and construction who confessed he was feeling guilty about it.

''This mill was similar to the one planned by Gunns in the Tamar Valley,'' says McMahon, ''and when I returned home I discovered that the Bell Bay plant was not to be a chlorine-free mill, as originally suggested, but a standard mill right in everyone's backyard on the banks of the Tamar River and adjacent to the woodchip mountains at Long Reach.''

McMahon realised that Launceston and Valdivia are almost geographic twins. They are on the same latitude, both are located at the confluence of two rivers, and they are subject to tidal changes.

It was no coincidence that two investigators from the Tasmanian government's pulp mill task force visited the Valdivian wetlands the same year, writing a report in 2006 on the pulp mill that noted a dramatic loss of bird life due to the ''severe and widespread decline of an aquatic plant'' but stating that the cause was ''inconclusive''.

Bob McMahon thought this was ''hogwash''. Earlier that year, a Chilean forestry student, Marianela Rosas, had visited the University of Tasmania's Launceston campus and given a lecture on this worsening Chilean disaster. There had been violent protest from local fishermen about effluent pumped into the sea, she said. The mill had been forced to shut down three times by regulators because of environmental concerns. And most tragically, all the area's beautiful black-necked swans had died or left.

In scenes more befitting a horror movie, she said some had even fallen dead from the sky, some crashing through car windscreens.

It was evidence Bob McMahon could not ignore and in June 2006 he returned to Chile to investigate first-hand. His sole local contact was Marianela Rosas, but it was a Chilean taxi driver named Luis who drove McMahon in from the airport who was first to raise the red flag. Luis had heard why McMahon was there and began waving his arms wildly .

''Los cisnes mueren! Los pajaros mueren!'' he shouted, words that sent a shiver down McMahon's spine. McMahon knew only a little Spanish but enough to know that ''cisnes'' was the word for swans, ''pajaros'' was birds and ''mueren'', was the word for death.

''Luis took his hands off the steering wheel and flapped his arms like a bird flying,'' McMahon wrote in his diary. ''He was almost in tears. It was obvious that something awful had happened there.''

Rosas introduced McMahon to Dr Eduardo Jaramillo, a professor of ecology and marine biology, the man who had traced the cause of the pollution in the Valdivian wetlands. McMahon recalls: ''The first warning signs of an environmental problem occurred late in 2004 when a dramatic decrease in the population of black-necked swans was noticed due to migration and an increase in mortality.

''The second sign was the demise of the aquatic plant luchecillo, the primary food of swans and other herbivorous birds, which occurred in the first three months of 2004. A month later, brown water began coming down the river into the city.''

Residents in Valdivia suspected the pulp mill 50 kilometres upstream was responsible and a scientific investigation confirmed that the cause was the mill's wastewater effluent.

Jaramillo explained that aluminium sulphate was being used as a reagent in treating the water and that produced aluminium hydroxide, which caused chemical particles to coagulate and drop to the bed of the wetlands. The high levels of sulphates, chlorines and heavy metals killed off the aquatic plants.

The luchecillo plant just turned into mucous. Autopsies of dead swans revealed they were about two kilograms lighter than healthy five-kilogram birds. Cygnets were stunted and would never be able to fly. The stomachs of the dead birds contained nothing but sediment and parasites.

Horrified by this ecological nightmare, Bob returned to Launceston and threw himself into the campaign against the Gunns plant. By 2007 he was addressing scores of public protest meetings, telling one gathering in West Tamar that their region had been set up to be a sacrifice zone.

''But the sacrifice zone is not restricted to the Tamar and its 100,000 people,'' he said. ''It extends into Bass Strait where the Bass Strait fishery could be wiped out. Who would want to catch, buy, let alone eat fish that is contaminated or perceived to be contaminated. Would you?''

He said the sacrifice zone would extend to all Tasmania's farmland, especially in the north of the state.

''The area of plantations required to feed this pulp mill, one of the biggest modern pulp mills in the world, will gobble up our farmland. Tasmania will have to sacrifice food production for tree plantations; perhaps all our food production if this dumb project is allowed to run its course. That is not a fair exchange. That is suicide. You can't eat trees.

''Tasmania produces 70 per cent of all Australia's processed vegetables. Already more than 20 per cent of our farms have gone under trees. The pulp mill, if it were to last a hundred years as pulp mills do, requires just about all of our farmland.''

McMahon quoted some figures that showed losses heavily outweighed gains. For every dollar the pulp mill generated, Tasmanians would lose three dollars through losses in food production, fishing, wine production and tourism. ''We are told the pulp mill would generate $6.7 billion over 30 years. In that time Tasmania will lose something in the order of $20 billion.''

By the time federal Environment Minister Tony Burke finally granted approval for the project last year, it was already too late for Gunns. The company was in financial strife and last month it told the stock exchange it might not be able to proceed with the mill.

Tellingly, the company accountants began listing the $250 million already spent as an ''expense'' rather than an ''asset''. When the company went into administration this week its shares, once worth $16, were at 2¢. On the night of that announcement Bob and Susie McMahon, who met as teenagers at a Hobart art school, opened a bottle of champagne to celebrate. They say they inflicted ''death by a thousand cuts'' on Gunns. They hope now that the struggle is finally over.

With two children and five grandchildren, the couple have returned happily to their previous routines, Susie crafting dolls that she sells on the internet and Bob enjoying the solitude of outdoor life. Named by Rock magazine as one of Australia's 50 top climbers, Bob McMahon is clawing his way up impossibly steep cliff faces again as an instructor and has resumed his ambition to walk, in stages, the entire coastline of Tasmania.

He says the long pulp mill dispute hampered Tasmanian progress for almost a decade. ''But our campaign is often misunderstood,'' he says. ''Everyone thinks it was purely environmental. It was actually a community campaign, a socio-economic campaign that began because of a great sense of injustice, because the costs and the risks were going to be borne by the community and the benefits, if any, were going to be gained by private enterprise with massive government support.''

Lawrence Money is a senior writer.