The moment she opens her mouth, her Greek accent startles you. You'd never guess that it's half a century since the 16-year-old raised in a small Athenian flat arrived in England. (She later upgraded to the US.) The accent, she tells the conference, "has been the bane of my existence, until one day I met Henry Kissinger and he said, 'You can never underestimate the effect in American public life of complete and utter incomprehensibility.'"
Yet when we sit down later — and after I have fended off her charming attempt to talk about me instead of her — Huffington explains that being Greek is a business asset. "Maybe being an outsider, I'm comfortable disrupting conventional ways of being. I don't have any allegiance to the current way of doing things."
She was perfectly placed to disrupt her first target, the media. Handily, she had money: in 1997 she amicably divorced the Texan oil billionaire Michael Huffington, after he told her he was bisexual. An author of many books, she had used her people skills to befriend half the American cultural elite. (She has been called "the most upwardly mobile Greek since Icarus".) And she foresaw, before almost anyone else, a future in which mostly unpaid writers would create new online media brands. In 2005 she founded The Huffington Post. The friends she recruited to blog for it ranged from Nora Ephron to Norman Mailer. In 2011 AOL bought the site for $315m. Huffington reportedly netted $21m, but stayed on as editor.
When Donald Trump began running for president, the Huff Post initially covered his campaign only in the entertainment section. Later it appended an editor's note to every article about Trump, calling him "a serial liar, rampant xenophobe, racist, misogynist and birther". But when I ask whether his victory surprised her, Huffington says no. She points me to her 2010 book, Third World America. "It's about the fact that many parts of America have become third world. They are the people who voted for Trump."
This year, possibly perceiving the pointlessness of journalism earlier than most, Huffington jumped from media to sleep. She herself had been a sleepless overachiever until 2007, when she collapsed and woke in a pool of blood from a broken cheekbone. She changed her sleeping habits, moving devices out of the bedroom and redefining bedtime as a phase of unwinding. Now she uses rituals such as hot baths and the writing of a nightly "gratitude list" to leave behind the day "with all of its problems and unfinished business".
It took her a while to see that sleep was a business opportunity. In 2014 she published the book Thrive. When she went around promoting it, "I found that this [sleep] is the one thing people wanted to talk to me about more than anything else in the book." (Huffington, unusually, can listen as well as talk.) So she wrote The Sleep Revolution and, last month, launched her "wellness company" Thrive Global. Central to its business model will be selling sleep.
I suspect this is a good idea. Most of us are tired. Charles Czeisler of Harvard Medical School estimates that average American sleep on work nights has declined over the past 50 years from eight-and-a-half hours to seven. Sleeping beside one's smartphone, as many people now do, doesn't help.
The problem is arguably embodied by Trump, who claims to sleep four hours a night. Huffington says he displays classic characteristics of sleep deprivation: impulsiveness, paranoia, an inability to process information. "He needs to get more sleep," she says, "and he needs to charge his phone away from his bedroom so that he doesn't wake up in the middle of the night and retweet Mussolini or attack the former Miss Universe."
But now, adds Huffington, ever more people are realising they have a sleep problem. In an unfortunate choice of metaphor, she says: "There's a collective awakening." Even Goldman Sachs and McKinsey use sleep specialists.
Huffington remains in part a journalist - that's how she sniffs out the zeitgeist - and the moment I finish interviewing her, she starts interviewing me about my sleep habits. I admit to feeling exhausted.
Four weeks later, I can report that Huffington has changed my life. Chez Kuper, bedtime now means bedtime: a phase of leaving the day behind. I cannot bring myself to write a "gratitude list" but I have stopped doing work-related reading in bed and no longer sleep beside my smartphone. And I do feel slightly less exhausted. I may go down in history as an early convert.