Yet he spoke with a Long Island accent, rattled around the Philadelphia area in a rusted '86 Volvo, and hit up a series of girlfriends for money. And he never seemed to come up with any hand-painted, original art.
The pieces he did produce were digital - mostly abstracts printed from computers, signed, and marketed online as $200 limited editions.
Several artworks on his Web site bear dates from 1999 to 2001. They certainly weren't produced in France: For most of that period, he was sitting in federal prison.
Sonnet is indeed accomplished. Not as an imported fine artist, but as the all-American con artist Richard Carl Grossman.
From 1992 to 1995, Grossman, now 57, pulled off one of the grander scams in recent local history.
Posing as a visionary psychologist, he defrauded a dozen financial institutions that had lent him nearly $18 million for a chain of dial-in, all-hours, $1-per-minute counseling clinics that never opened.
Much of that cash went into construction of an enormous Main Line mansion, a 27,000-square-foot structure so over-the-top that its roof had to be cut flat halfway up to meet Tredyffrin Township's height restrictions.
Grossman pleaded guilty to fraud and money laundering, and spent 32 months in prison. He emerged late in 2001 and, while still under federal probation, began crafting his next persona.
As Luc Sonnet (pronounced so-NAY), he boasted of hanging out with Andy Warhol in 1980s New York. Of dating supermodel Kate Moss. Of having Rolling Stones guitarist Keith Richards' number programmed in his cell phone.
He invited acquaintances to visit his chateau in France. He professed to be Ivy-educated. He hired a crew of graduate students to film him proclaiming himself a digital art pioneer, then posted the clip on YouTube, calling it a preview of a PBS documentary about him.
While many who encountered him found his claims improbable, even laughable, a good many others took the bait. A sample:
