"Portrait of an Artist (Pool with Two Figures)" is considered by many to be David Hockney's greatest work. The painting was featured in an international tour last year that included London, Paris and New York's Metropolitan Museum of Art. Now it's poised to make the 81-year-old Hockney the most expensive living artist.

"CBS This Morning Saturday" co-host Anthony Mason got a chance to look at the Hockney masterpiece up close before it hits the auction block at Christie's Thursday night, where it's expected to sell for an estimated $80 million. If it does, it would shatter the record set by Jeff Koons' "Balloon Dog," which sold for $58.4 million in 2013.

In an interview at his Los Angeles studio two years ago, Hockney told Mason he doesn't know why it's been so popular over the years, and aptly pointed out, "If there were a formula for that, there'd be a lot more of them, wouldn't there."

Hockney said he was drawn to California by the sunshine, far from his hometown of Bradford, England, which he described as having a "gothic gloom." California is where he found his sense of color and where he developed a fascination with pools.

"It's always an interesting thing. How do you paint water? How do you paint something transparent?" Hockney said.

"Portrait of an Artist (Pool with Two Figures)" is perhaps Hockney's most famous pool picture. It's also the only one to include his other most prominent theme, the double portrait.

"This one is actually a very personal story. Because it's about his love and his lost love. Or his love that he's about to lose," explained Alex Rotter of Christie's auction house.

The story is told in the 1974 film, "A Bigger Splash," which captured Hockney working on a first version of the painting, which he'd later abandon and destroy, then showed him photographing his estranged lover, Peter Schlesinger, for the second painting, which he finished.

Although the British pop artist became popular in America, for a long time art historians were unsure where to place Hockney.

"The market took a long time to come around, because he found his real – his language, just when he moved to America. And then was seen in a funny way in the context of American paintings," Rotter said. "He didn't fit anywhere."

But at 81, Hockney, who's still at work, may have lived long enough to become the priciest living painter.

"You just go on and on 'til you fall over," Hockney said. "I'm still a smoker. I mean I just go on and one day I'll fall over, yeah. I don't mind."

Thursday's winning bid is expected to more than double the previous record paid for a Hockney painting, which was $28.5 million at a Sotheby's auction earlier this year.