It is about an hour after I meet Josh Harris that he asks if I want the real story. So far we’ve skated over his life as a tech mogul in the 1990s, worth more than $50m at his peak. We’ve talked about how ahead of his time he was with an internet TV company called Pseudo Programs, which tried to merge video and chat about 10 years before most people had broadband. We’ve touched on the six-month project in 2000 with a former girlfriend, in which he rigged his plush New York loft with cameras and broadcast absolutely everything — including sex and bowel movements — over the web.

I ask how he came from that to a grubby apartment in Las Vegas, scraping $650 or so a month from online poker to live in this sketchy neighbourhood, a 10-minute walk from the Strip.

He moved in to the second-floor unit, part of a row of flats built by the mob in the 1950s to house casino entertainers, about 18 months ago but the breeze-block walls are almost bare and there is very little furniture: just a workbench in the back room and a plastic table and chairs in the front.

From his window by his galley kitchen he looks across low roofs to the observation tower of the Stratosphere, the tallest building west of Mississippi. He sleeps in a bag on a mattress on the floor, a knife by his side.

He leans closer, looks at me straight and asks if I’m ready. Really ready.

For the next couple of hours I hear about his relentless pursuit by the FBI: how a link to an art installation at the World Trade Center, pre-9/11, has caused him to be watched ever since.

Surveillance by the state is why he lives alone, he says, and has gone without a girlfriend for a decade. And it is why he has cut off all contact with his three sisters and three brothers. He asks — or rather demands — that I make no attempt to speak to them.

“There are men in rooms who are deciding how much trouble it would be to have you not be part of the planet earth,” he says later, over coffee at Vickie’s, a local diner.

If that moment ever comes, he wants it to be quick. He bends closer to my voice recorder. “Two taps to the back of the head by a professional, please.”

Harris, 56, had an unconventional childhood. Raised in Ventura, California, he was the youngest of seven children and described by one brother in a 2009 documentary as “a goofy kid.” His mother put in long hours as a social worker and he also didn’t see much of his father, a CIA agent. He says he raised himself, mostly via the TV set.

After college in San Diego he made his way to New York, got a job at a research company then struck out on his own with Jupiter Communications, which measured online traffic. He quit Jupiter in 1994 to found Pseudo but when his old company went public on Nasdaq in 1999 he still owned about 15 per cent, making him a multi-millionaire.

Harris in front of his apartment block © Philip Cheung
Garbage skip outside the building © Philip Cheung

By then he was running chat rooms for Prodigy, the internet service provider, and getting deeper into New York’s avant-garde art scene. His biggest production was “Quiet: We Live in Public”, a month-long “experiment” at the turn of the millennium, in which 100 or so volunteers lived in capsules in a six-storey warehouse on Broadway. The facility had a mess hall, an interrogation room, a shooting range and a chapel. It was open to the public and it was wired, top to bottom, with webcams. The city’s Museum of Modern Art considered it much an encapsulation of the era as Truman Capote’s Black-and-White Ball of the mid-1960s. Police shut down the project on New Year’s Day 2000.

According to Harris, he became a person of interest to the FBI because of his association with Gelatin, a performance-art troupe from Vienna. In March 2000 the group claimed to have removed a window from the 91st floor of the World Trade Center’s North Tower, inserted a prefab balcony then walked out on to it, naked, one by one. Harris says he filmed the stunt from a helicopter he had hired.

The New York Times ran a story on the affair the following August, in which Harris was quoted as a keen and unrepentant facilitator. The story was prompted by a Gelatin show documenting the event — scheduled for September 11 2001.

Door-less closet © Philip Cheung
Fridge © Philip Cheung

Harris reasons that the show’s date and its title — “The B-Thing” — might have suggested that Gelatin knew about the Bin Laden attack in advance. At least one of the group’s members is of Arab descent, he notes. What is more, the group insisted on keeping all video, audio and still photography of the event — all of which left the country to parts and people unknown. As Harris wrote to a judge in 2011, the FBI would have been irresponsible if it did not “make absolutely sure that the . . . balcony installation was simply a harmless art prank”.

Is all the stuff about surveillance in his head? Harris wouldn’t be the first person to lose his bearings, living alone in Vegas. Yet some of the tales of pursuit are compelling — odd encounters on a plane to Panama, on a fishing boat off Long Beach and in a coffee shop in Los Angeles. He says he was even monitored by security forces in Ethiopia, where he took off for a year in 2007 with his last $8,000. (He had lived in Addis Ababa for three years as a boy). The money more or less evaporated after the dotcom crash, when Pseudo and Jupiter tanked, and he spent heavily on his art projects.

The most bizarre surveillance story is the one featuring a couple of German Shepherd dogs he picked up after moving to an apple farm in 2002 in upstate New York. Harris says he made the mistake of leaving the dogs alone with one of the cats he had brought with him from Manhattan. He returned to find the cat dead and one of the dogs looking sheepish. Stricken with grief and anger, he grabbed his rifle and was about to pull the trigger when there was a knock on the door. It was a handyman who had completed a job on his house a few months earlier. The man took the dog.

Harris lying on his bed © Philip Cheung
Bathroom © Philip Cheung

Harris says he finally figured it out a few months ago, on one of his daily walks along Sahara Avenue, which runs the width of Vegas. The place must have been rigged with cameras, and the contractor/agent was watching nearby.

“Look, I play poker all day long, I do numbers. When that hand comes in, I wonder about the algorithm. If nothing else, I guess they’re dog lovers.”

Harris is a warm host but living alone has taken its toll. At one point he hawks and spits into the kitchen sink. His only company is Pretty Bird, a budgie he got from his landlord. A few small piles of clothes are set out on the bench in the bedroom, and a couple of coats are hanging in a built-in, door-less closet. By the back window he has laid down plastic sheeting, so he can hear an intruder.

Holding a mug © Philip Cheung
Pocket knife that Harris keeps next to his bed © Philip Cheung

There is one book by the bed: Tao Te Ching by Lao Tzu. He’d get more, he says, but cannot afford new reading glasses.

Outside, posing for pictures, he nods at his next-door neighbour. “That’s the most interaction I’ve had with that guy,” he says.

Harris still dreams of putting on another big show. He hopes to fill Tate Modern in London with what he calls the “Cybership” — a vast “human chicken factory” in which volunteers would live in cages, their lives monitored and controlled by people watching online. It would be a glimpse of “the singularity,” he says: the moment when machines outsmart the people who built them. Ray Kurzweil, the futurist who popularised the term, reckons it will occur in about 30 years. Harris thinks much earlier: autumn 2024.

His budgie, Pretty Bird © Philip Cheung

“When you get a computer in for customer service, instead of you being annoyed at it because it’s stupid, it’ll be annoyed with you.”

For now, though, he’ll keep walking the Sahara, raking over the past.

“This has been an unbelievable 10 years of my life,” he says, panning back to when the money ran out. “I look at the venture capitalists in New York, they’re very good at what they do, but God — grist for the mill, or what? If I was 18 and I could look forward to this particular precipice in my life? Damn straight — this is the super groove.”

Ben McLannahan is the FT’s US banking editor

Photographs: Philip Cheung