* France's three richest tycoons pledge 500 million euros
* Most shunned a restoration fundraising campaign two years ago
* French authorities, companies follow billionaires
By Inti Landauro and Caroline Pailliez
PARIS, April 16 (Reuters) - For years Notre-Dame cathedral was caught in a dispute between the city's archdiocese and the French state over who should pay for repairs to its crumbling gargoyles, collapsed balustrades and weather-eroded Gothic facades.
Awaiting funds, Church officials used plastic pipes to drain water from one of the world's most admired landmarks and created a "stone cemetery" from the fallen masonry.
On Tuesday, hours after flames had toppled the cathedral's once towering wood-framed spire and gutted the roof, French tycoons had already pledged hundreds of millions of euros for restoration, as had some of the country's best-known companies.
Before the end of the day, donations had exceeded 700 million euros ($790.93 million).
"It's a shame," said Philippe de Cuverville, general director for the Paris archdiocese in charge of economic affairs. "We tend to wait for things to become catastrophic before we take care of them. It's just human nature."
The outpouring of funds came amid a sense of national grief over Monday's massive blaze at the 12th century Gothic cathedral in the heart of Paris.
Tuesday's largesse was in sharp contrast to fundraising just two years ago, when the diocese appealed for 150 million euros to help restore the cathedral, some of which dates to the middle of the 12th century.
The government of former President Francois Hollande agreed to contribute 4 million euros annually over a 10-year period, double the 2 million euros the diocese said it would raise.
That still left the church nearly 100 million euros short, prompting the Friends of Notre-Dame charity, set up by the archbishop, to undertake fundraising overseas. He warned then of a grave risk that parts of the cathedral's exterior could break up.
"We hoped that if we managed to raise more we would convince the government to raise its promises and do more work," de Cuverville said.
The first pledge on Monday evening, as the blaze was still burning strong and consuming the oak-framed roof.
Francois-Henri Pinault of Kering Group, owners of Gucci and Yves Saint Laurent, offered 100 million euros. Soon after, his arch-rival Bernard Arnault of luxury group LVMH pledged double Pinault's sum.
The Bettencourt-Meyer family, the largest shareholder in the L'Oreal cosmetics empire, offered 200 million euros, while oil and gas producer Total pledged 100 million. The City of Paris said it would unlock 50 million euros.
French prosecutors investigating the blaze said it was probably caused by accident. The Paris prosecutor has opened an investigation into "involuntary destruction by fire" and police began questioning workers involved in the restoration.
Jean-Michel Leniaud, head of the science council at the National Heritage Institute, said the blaze was the result of carelessness and neglect that stemmed in part from what he called a puerile conflict between the state, which officially owns Notre-Dame and is avowedly secular, and the Church.
"The lack of real maintenance and daily attention to a major building is the cause of this disaster," Leniaud told Catholic newspaper La Croix. "The responsibility is completely collective because it's the most collective monument in the country."
"We imagine that our patrimony will last forever, without us doing anything," he said.
Disputes over the financing for Notre-Dame's restoration go back two centuries to the last major project carried out during the 1800s, when architect Eugene Viollet-le-Duc designed and added the cathedral's spire, historians say.
"There was a continual cry for funds (in the 19th century) because the needs were so great for a building of that size. Necessarily it required enormous expenditures of money just to maintain it," said Professor Kevin Murphy at Vanderbilt University in Nashville, Tennessee.
Designing the rebuild will see two competing forces run up against each other, he said. "Imperative one is to preserve the building as an icon of French architecture, and the other is to make it serviceable for its purposes as a place of worship."
Reporting by Inti Landauro and Caroline Paillez Additional reporting by Richard Lough Writing by Inti Landauro and Richard Lough Editing by Luke Baker and Frances Kerry