By Polina Devitt and Oksana Kobzeva

MOSCOW (Reuters) - Last month, three major banks rescued industrialist Igor Zyuzin's coal and steel firm Mechel from what would have been Russia's biggest ever corporate collapse.

The bailout was unusual in a country where so many decisions often lead back to President Vladimir Putin or his inner circle. Zyuzin has long been an outsider, a multi-millionaire who built his business empire by staying out of the reach of the Kremlin. Eight years ago, Putin publicly humiliated Zyuzin after the businessman failed to show up for a meeting.

The rescue deal shows how much Russia has changed since then. The commodity price slump and sanctions over the conflict in Ukraine have hurt the economy and unsettled Putin's grip on power.

Thirteen people involved in the Mechel rescue deal have given Reuters new details about the Kremlin's involvement in the bailout. Some said the decision to save Zyuzin's company was taken mid-way through last year when the Kremlin realized that the firm's failure could threaten two of the pillars of Putin's Russia: social stability and the financial health of a bank close to the Kremlin.

The Kremlin, those sources said, feared that if Mechel went bankrupt it could lead to layoffs among the firm's 66,000 workers, many of them in rust-belt regions where local TV has shown riot police training to put down worker protests.

"There was a lot of politics in this situation," said Maxim Poletayev, first deputy chairman of Russian state lender Sberbank, a major Mechel creditor. "No one wanted to save Zyuzin, but everything had to be done without social unrest."

The Kremlin was also worried about Gazprombank, one of Mechel's biggest creditors. The brother of Putin's son-in-law sits on Gazprombank's board, and the bank has previously financed projects for Kremlin allies. People familiar with the Mechel debt talks said the Kremlin feared Gazprombank would struggle to cover its exposure if Mechel failed.

Those involved in brokering the deal included Igor Sechin, a Putin lieutenant and chief executive of state-owned oil giant Rosneft, according to one source.

Sechin told Reuters he did not want to disclose his discussions with Putin, but said he was aware of Mechel's difficulties.

"I did not feel any great joy about this. I thought, and I think, that Mechel deserved support, which was given in the end," he said.

Zyuzin declined to answer questions for this story. A person familiar with his thinking said that he was driven by a sense of responsibility to his company and its workers.

Mechel denied it sought or received any direct intervention from the Kremlin. It said its creditors acted on a commercial basis only, and that the company was helped by a fall in the value of the rouble, which reduced its debt in dollar terms.

Kremlin spokesman Dmitry Peskov denied any instruction was given to rescue Mechel. "Such discussions are not taking place in the Kremlin and are not agreed with the Kremlin," he said.

Gazprombank did not respond to Reuters questions, while state lender VTB, another big Mechel creditor, said its decision to restructure Mechel's debt was motivated by business interests. It called the idea of political intervention "pure nonsense."

MODEST TASTES

Russian business moguls mostly fall into one of two camps: long-standing Putin associates, many of whom, like the president, once worked in the security services; and entrepreneurs, who favor a market economy but remain loyal to the Kremlin.

Zyuzin, 56, is in neither. A former mine overseer, he is known for charting his own path and his modest tastes. He owns only one house and drinks $12 bottles of New Zealand wine, according to a person who knows him.

He also hates debt, and in his early days avoided borrowing from state-controlled lenders. Around a decade ago, though, Mechel borrowed to modernize its plants and expand internationally.

In 2008, allegations surfaced that Mechel was selling to foreign customers more cheaply than at home. Putin, who was then prime minister, summoned Zyuzin to a meeting.

The businessman sent word he could not come because he was ill. Video footage of the planned meeting shows Putin, his face taut with anger. If Zyuzin did not get better, "We'll have to send a doctor to him to clear up all these problems," Putin said. Mechel's share price plunged.

Later that year, when the global financial crisis hit and coal and steel prices slumped, Mechel struggled to repay its loans. In 2014, some of the firm's major creditors decided they could not keep restructuring Mechel's debt. The creditors tried to renegotiate the loans, offering to take Mechel equity in return. But Zyuzin would not give up any of his company.

To break the deadlock, creditors launched legal action to recover their money. One industrial source said the government wanted the company bankrupt “to set an example."

Zyuzin fought. To make sure Mechel did not run out of money, he insisted on personally approving any spending over 1 million roubles ($15,617), according to a second source who knows the Mechel boss.

LOBBYING OPERATION

Sometime in the last year or 18 months, a group of Kremlin insiders began to push Zyuzin's cause with Putin.

The insiders included Putin lieutenant Sechin, according to one source familiar with the deal. That source and one other said Vladimir Yakunin, then boss of Russia's state railways, and Alexander Shokhin, head of the Russian Union of Industrialists and Entrepreneurs, also lobbied on behalf of Zyuzin.

The involvement of Sechin and Yakunin – two of the most influential powerbrokers in Putin's Russia – has not been reported before.

Yakunin told Reuters "the country's leadership" had raised the question of Mechel after a meeting with a large industrialist union.

A representative for the union declined to comment.

After the lobbying, the banks' attitude to Mechel changed dramatically. A source at one of the creditor banks said the law suits were suspended in September last year, opening the way for a deal in which creditors deferred repayments and wrote off most of the penalties Mechel owed. An agreement was approved by Mechel shareholders on May 30.

"Zyuzin decided it was a miracle," said the source who knows the Mechel boss.

Of all Mechel's creditors, Gazprombank was the most exposed. Russia's third biggest lender by assets, it has close ties to Putin's inner circle. Sergei Ivanov, son of Putin's chief of staff, sat on the Gazprombank board until earlier this year. Yuri Shamalov, brother of Putin's son-in-law, Kirill Shamalov, is head of Gazprombank's biggest shareholder and also sits on the bank's board.

The $1.8 billion Mechel owed Gazprombank as of February this year amounts, according to Reuters calculations, to about 20 percent of Gazprombank's current capital. Russia's central bank rules stop a bank lending more than 25 percent of its capital to a single client.

Two banking sources said Moscow pressed for a deal because it feared Gazprombank would be damaged by a Mechel bankruptcy.

Under the deal, Gazprombank bought a stake in Mechel's Elga coal project, so Mechel could use the revenue from the sale to pay back Sberbank.

WORRIED WORKERS

Outside, Mechel's plant in the city of Chelyabinsk one recent afternoon, workers filed out at the end of a shift, past a long metal panel that featured photographs of employees named as "champions of productivity."

Vladimir Ponosov, a trade union boss at the plant, said a Mechel collapse would have hurt workers. He said over 110,000 people depended, directly or indirectly, on Mechel for a living.

"Some would have found work, but we would have faced big difficulties," Ponosov said.

He said the last two years had been "psychologically very difficult. The people expressed their concerns, but there were no protests or demonstrations, because wages were paid on time."

But authorities are still worried about unrest, especially in Russia's rust-belt. In May, state television showed riot police in the Chelyabinsk region training to put down potentially violent protests. Police officers playing the role of protesters built barricades out of car tyres, threw stones and sticks, and took an officer hostage.

VTB Chief Executive Andrei Kostin told Reuters that while the Mechel deal was decided by the creditors, "Of course it (the government) wanted us to reach an agreement. The social problem is important to it."

When Zyuzin's troubles first started, he stuck a quote on the wall of his office: "Loans, like sins, weigh on your soul."

In June, he attended an investor conference in St. Petersburg, where Russia's political and business elite came to hear Putin speak. In a corridor, a Reuters reporter spotted Zyuzin, once the scourge of Russian bankers, greeting an executive from lender VTB with an enthusiastic hug.

(Additional reporting by Natalya Shurmina in Chelyabinsk, and Oksana Kobzeva, Katya Golubkova, Darya Korsunskaya, Svetlana Burmistrova, Vladimir Soldatkin and Gleb Stolyarov in Moscow; Edited by Simon Robinson)