DENIS Wagner was on holiday in New Zealand when the flood hit, gazing at a television screen in a hotel room in stunned amazement as cars floated down the street of his home town of Toowoomba.

“I couldn’t believe it was happening,’’ he recalled years later.

“It didn’t seem possible in Toowoomba.”

It was January 10, 2011 and that angry brown tide which Wagner watched surging through the streets of his city 700m above sea level was the first sign the state of Queensland was about to experience one of its worst natural disasters in its history.

More than seven years on, it’s easy to forget just what a catastrophe that flood represented.

The next day 59 people were still missing.

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Thirty crumpled cars were wedged underneath the Grantham Railway Bridge, a senior police officer described the scene as a “war zone’’ and hundreds of victims, like Ken and Frances Arndt who fled waters in their ute and then clung to a tree before being rescued, had endured the most horrific experience of their lives.

Twelve people perished in Grantham that day. Thirteen more died throughout Toowoomba and the Lockyer Valley.

Wagner, whose family had settled the Lockyer Valley/Toowoomba region in the mid-19th century barely three decades after John Oxley had sailed up the Brisbane River and begun the European settlement of Queensland, was dumbfounded.

‘’Like everyone in our community, we felt sympathy for those families who had lost loved ones.’’

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Three years later his stunned family stood directly accused of being responsible for each of those 12 deaths in Grantham – a “municipal murder,’’ as Sydney radio personality Alan Jones described it.

On Wednesday, as Justice Peter Flanagan delivered the verdict in the Jones defamation case, Denis Wagner – representing himself and his three brothers John, Denis, Neill and Joe – gave voice to more than six years of hurt and frustration.

After the first cursory reading of the judgemnt, Wagner clearly found some satisfaction in the strong wording.

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“Justice Flanagan found that the statements made by Alan Jones were self evidently vicious and spiteful,’’ Wagner pointed out.

“The judgment found that Jones was motivated by a desire to injure, and it also found that Alan Jones was wilfully blind to the truth.’’

Wagner, who also noted that the judgment found some of Jones’ assertions were simply “nonsensical’’, said the brothers had no choice but to take Jones on.

“We decided to take a stand against this abhorrent, vicious and deceitful, spiteful behaviour,’’ he said.

The verdict may give the Wagners some satisfaction, but it won’t heal all the wounds of a family whose business ventures have, in the view of the State Government, made the most significant contribution to Queensland’s regional development in the past 150 years.

The Wagner fortunes might be said to have begun in the mid-19th century in a stone mason business which helped furnish the University of Queensland with its sandstone blocks.

But it was not until family patriarch Henry yarded three of his sons – John, Denis and Neill, (and later, Joe) – into a construction business that the Wagner’s extraordinary business acumen began to become apparent to the public.

That business which began in 1989 soon blossomed out of a simple concreting plant in Toowoomba to many plants that would crisscross the world.

The Wagners have supplied construction materials to lay pipelines in Russia and built bridges in America.

They developed and marketed a new type of environmentally friendly concrete which will change the construction industry around the world, and they stunned the nation in 2014 by opening the international Wellcamp Airport which they had carved out of a cow pasture outside Toowoomba.

The Wagners have won countless awards but one is particularly dear to Henry.

In 2009, the family company was officially recognised by Premier Anna Bligh’s Labor Government at the Smart State Business Awards as the one business making “the most significant impact on regional Queensland in the state’s 150 year history.’’

That widespread respect and admiration, reaped by generations of hard work and nation-building, began to unravel only a few months after the Grantham floods catastrophe, but the genesis of the onslaught had nothing to do with the actual flood itself.

The Sydney-based broadcaster Alan Jones was in constant contact with former journalist Heather Brown, who owned a property next to the site of the Wellcamp Airport which had been owned by the Wagners since 1994.

The land had been rezoned as a Major Industry Precinct in 2001 but in 2011 was still little more than a pasture and a quarry.

Brown believed some of the land at the site which was zoned “heavy industry’’ was earmarked to become a toxic waste dump, and complained about it to Jones on air.

“It was all nonsense,’’ Wagner recalls.

”This sort of stuff was being put on air on the Jones program and we tried to explain it wasn’t true, but in the end there was little we could do about it.’’

By June of 2012, with an application by the Wagners to build the Wellcamp Airport now public and formally before the Toowoomba Council, Jones’ attacks on the family escalated.

Jones was opposed to the airport and so were others in the community.

“It was just extraordinary what he was saying,’’ Wagner recalls.

“We were accused of bribing the council and getting involved in corruption and all sorts of extraordinary things while all we were doing was building and airport for the public on our land.’’

But Jones was getting traction. Many locals who were initially supportive of a major airport being built just 16km west of the Toowoomba CBD became hesitant about the project.

The Toowoomba Chamber of Commerce proposed a “town hall’’ type meeting where Jones, and one or two of the Wagners, could share the stage and discuss the project and answer questions, but Jones demurred.

The Wagners, in turn, wouldn’t go on air with Jones because the brothers knew who controlled the microphone, and figured they wouldn’t stand a chance.

So, in a public relations exercise, the Wagners announced an open day at the airport in late 2013 during construction.

The turnout was impressive as 18,068 locals arrived to marvel at the formation of the airfield and ongoing work while learning about what it would mean in terms of economic opportunities.

The public mood swung back to the Wagners and by September 2014, at another open day, a massive crowd of 27,000 people turned up, cementing the support for the airport.

But, by the time the airport was completed, Jones had opened up a new front in his attack on the family.

Wagner had heard several weeks after the flood that there was some gossip in the Lockyer Valley that the Wagner-owned quarry had caused a large build-up of water, that a levee had burst and that the resulting wave of water had caused the town’s destruction.

“I rang Steve Jones (then the Lockyer Valley Mayor, now deceased) and we talked about it,’’ he recalls.

“Steve said he had not heard about it but he believed there was just nothing in it – that it wasn’t true.

“I really didn’t think much more of it after that – people will talk and I think after an event like that, people are looking to blame someone and I suppose you can understand that.

‘’I was confident our operation could not have caused the flood so did not dwell on it.’’

That same year, the Queensland Flood Inquiry of 2011, in which the Wagners didn’t field a personal legal representatives because they believed they had nothing to contribute, came to the same conclusion.

The inquiry commissioned a report by hydrologist Dr Phillip Jordan who found that the Wagner quarry actually swallowed some of the flood water and both delayed the flood and slightly reduced its impact.

But by late 2013 journalist Nick Cater, working for The Australian (the defamation case against Cater, heard in conjunction with the Jones matter, was dismissed by Justice Flanagan) was looking at another independent hydrological engineering study commissioned by his newspaper, and becoming convinced the Queensland Flood Inquiry had got it wrong.

The new report suggested the collapse of a levee, said to be three to five metres high and 380m long, was a possible source for the intensity of the flood.

Jones was quickly on board with the stories which Cater was breaking, and which were picked up later and graphically illustrated on Channel 9’s 60 Minutes.

In around 32 broadcasts between 2014 and 2015, Jones was relentless in his accusations which, in the aggregate, were extraordinary.

Jones was alleging the Wagner Quarry not only caused the deaths but the family were somehow covering their tracks by bribery and corruption in a massive conspiracy roping in then Premier Anna Bligh, Deputy Prime Minister Warren Truss, former Federal Industry and science Minister Ian Macfarlane and future Deputy Prime Minister Barnaby Joyce.

The accusations shook Denis and his brothers, but it was their mum and dad, Mary and Henry, whom they were most worried about.

“Dad would ring me on some mornings and say “did you hear what he’s saying, do you hear what this bloke is saying about us?’’ Wagner recalls.

“And I would say, ‘dad turn it off, please, just don’t listen to it’.’’

Henry was angry, Mary more hurt and perplexed, but the frustration and anger the brothers felt at not being able to defend their name was growing steadily.

Wagner actually met Jones at a mutual friend’s house in Toowoomba way back when the attacks on the airport were under way and tried to persuade him to see the other side of the story.

But while the meeting was cordial, the attacks kept coming.

“It just kept coming, broadcast after broadcast, and you would just try to tune out but you would also wonder why this is happening to you.’’

When the Grantham Flood inquiry was announced by Premier Annastacia Palaszczuk in May 2015, Wagner and his brothers were deeply supportive.

Denis, who had been involved with the operations of the quarry, was the one designated to give evidence and did so, calmly and in a forthright manner, over three days.

That inquiry, headed by Walter Sofronoff QC, now president of the Queensland Court of Appeal, totally exonerated the Wagners.

Hydrologist Dr John Macintosh, in findings which mirrored some of Dr Jordan’s original work, concluded the quarry may have actually mitigated the flood slightly but, unquestionably, did not cause it.

Sofronoff declared the entire flood a “natural ­disaster that no human agency caused, or could ever have prevented ...’’

Towards the end of the hearings which took place in the town of Grantham, Sofronoff asked if Wagner believed the family had been the victim of “opprobrium’’ in the years following the flood.

With admirable restraint, Wagner said he believed that to be true, and then added tellingly, in a terse voice: “I do believe there are some terribly vindictive people in media, particularly in radio media, that have very little regard for the truth.’’

The comment was clearly targeted at Jones who, a short time later, was served notice that the family would sue.

The Wagners have contributed a great deal to the state and, with this verdict, they contribute something more, though it may be of cold comfort to them.

The Wagner/Jones case offers us a salutary lesson in the dangers of how idle gossip and uninformed speculation can turn into a dangerous conspiracy theory, and cause incredible damage to innocent parties.