Julian Niccolini, left, and Alex von Bidder at the new Four Seasons in New York.

The day Lehman Brothers filed for bankruptcy — Sept. 15, 2008 — the Grill Room was practically empty. Julian Niccolini, the maitre d'hôtel and a co-owner of the Four Seasons restaurant, was taking calls nonstop. The calls came from Wall Street executive assistants, canceling the reservations of the so-called Masters of the Universe who had suddenly become the Masters of Nothing.

The cancellations piled up, and those who kept their reservations tempered their spending. "Lots of iced tea," Mr. Niccolini said, "and very little wine sales."

Lehman's bankruptcy, the largest in the country's history, marked the end of an era and brought the financial world to the brink.

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"Everybody thought that it would never end, and everybody was drinking the most expensive wine on the menu," Mr. Niccolini said. "And then that day happened, and it was like the end of the world."

If there is a person with a unique and candid perspective on the cultural swings on Wall Street since the crisis, it might be Mr. Niccolini. He is a restaurateur to the titans of finance and a raconteur whose own wanton conduct — a sexual abuse case that ended in a misdemeanor plea — makes him something of a smudged window into an otherwise an opaque world.

Mr. Niccolini has been serving lunch to Wall Street's elite since 1977 and can relay by memory the table numbers of chief executives like Jamie Dimon of JPMorgan Chase and Stephen Schwarzman of Blackstone, and the drink choices of Pete Peterson, Mr. Schwarzman's co-founder in Blackstone, who had been President Richard M. Nixon's commerce secretary.

"Oh, my God, Bruce Wasserstein," Mr. Niccolini said, invoking the late investment banker, who pioneered the art of the hostile takeover. "Every time he didn't get the right table, I got a phone call from his assistant, my God, trying to shoot me down."

A lot of ink has been spilled over the past 10 years about whether Wall Street's fundamental ethos has changed. Did the near-death experience itself — or the regulations that came after — fundamentally change the souls of Wall Street's upper echelon?

Many on Wall Street like to say so. Lessons have been learned, they say.

But Mr. Niccolini has had a table-side view of moguldom for decades, and he knows what he saw.

In the aftermath of the crisis, whether out of a sense of guilt or anxiety about sending the wrong message, there were attempts at frugality. "People started to watch what they were spending," he said. And nobody wanted to be showy: "Private events went way down."

But that thriftiness evaporated in a matter of months. "Everything became the same again, because these people have money," Mr. Niccolini said. "Don't forget that part. They have money. They want to spend money."

Bonuses returned to Wall Street by the end of 2009 — Goldman Sachs's bonus payments reached $16.7 billion, the highest level in its history — and the financial power players returned to the Four Seasons.

"You know, half the people in this place could be prosecuted," Oliver Stone, the film director, told me with a sense of glee in 2010 as he surveyed the Grill Room. It was just before the premiere of "Wall Street: Money Never Sleeps," in which he revisited Gordon Gekko's universe and a post-crisis "Wall Street."

Even those laid low by the crisis, like Dick Fuld, the final chief executive of Lehman Brothers, found refuge at the Four Seasons. "He used to come once in a while," Mr. Niccolini said. "He was not treated any different than any other people."

There have been longstanding changes, of course. But the one that stands out to Mr. Niccolini reflects a change in societal attitudes more than industry ideals.

"Some of those guys, like Lewis Glucksman from Lehman Brothers, every time he used to come to the Four Seasons, yes, of course he had three-martini lunches," Mr. Niccolini said of the now deceased 1980s Lehman chief executive, who helped groom Mr. Fuld. "There was nothing wrong with that, you know? Because those people had some kind of different constitution. There were people that could actually drink a three-martini lunch and go back to work."

The only people who didn't drink were Mr. Peterson and Mr. Schwarzman, Mr. Niccolini said. "But Sandy Weill," he said, referring to the former head of Citigroup, "he enjoyed his cocktail."

He's less sanguine about the move toward more casual dress: "I'm waiting for Dan Loeb to show up with sneakers on," he said referring to the activist hedge fund manager, with a quick laugh. "I mean really, no. It's still Park Avenue, believe it or not."

Whether over drinks or duck, part of what long mattered about the Four Seasons was being there.

"It was important to be seen, to carry on negotiations privately but in sight of others," Paul Freedman wrote in his 2016 book, "Ten Restaurants That Changed America." The Four Seasons, with its cathedral ceilings, allowed patrons to "see their neighbors, hear their own confidential conversation without difficulty, and not be overheard — all in a serenely luxurious setting," he wrote.

Mr. Freedman's book discusses the Four Seasons in the past tense. It closed that year, losing its place in the Seagram Building on Park Avenue, but with plans to move a few blocks away. Just a few months before, Mr. Niccolini pleaded guilty to misdemeanor assault. The plea stemmed from an allegation that he had sexually abused a woman the year before during a party at the restaurant. Mr. Niccolini was also the subject of a sexual harassment suit from a former waitress that was resolved in 1992, although the details were not made public.

"I've dealt with it," he said. "It is something of the past."

Now the Four Seasons has returned, reopening just a few weeks ago. The past has not affected business, Mr. Niccolini said, his restaurant is already pulling in the moguls again.

And so the Masters of the Universe — or at least their assistants — are lining up their reservations once more.

"Everybody wants to pick their own table," Mr. Niccolini said, listing the names of Wall Street luminaries who had visited the restaurant before its opening to claim a spot.

"You know what that means? They are saying: 'I have more money than you. I have more power than you. I am in charge,'" he said.

"It's about money. It's about power," he continued. "It hasn't changed. In fact, it's getting much worse."