A look at luxe homes that recently traded without ever being listed

The year was 2016. The billionaire was Len Blavatnik. And the house was the Wildenstein mansion, a 20,000-square-foot property at 19 East 64th Street.

After a handshake deal, Blavatnik thought the house was his — until heirs to the art gallery fortune accepted an offer for $79.5 million from HNA Group. Blavatnik sued and lost.

But the story doesn’t end there.

With the Chinese conglomerate under pressure to sell off its assets, the billionaire pounced, paying $90 million for the house in February before it ever hit the open market.

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Like a growing class of uber-wealthy New Yorkers, Blavatnik tapped into a trove of residential listings that the rest of the world has no access to.

While off-market deals have always existed — especially in the uppermost echelon of the market — a recent uptick in whisper listings has caught the eye of the Real Estate Board of New York, which is now considering cracking down.

In March, REBNY’s residential board of directors — which sets rules for how listings must be disseminated to brokers — drafted a proposal that would have required agents to turn down whisper listings altogether. But the move elicited immediate blowback from many of the city’s largest residential firms, prompting the board to scrap its plan.

“You can’t legislate what the seller wants to do,” said one brokerage chief. “I’m doing what my seller wants, not what REBNY wants.”

Check out more about whisper listings in NYC