Image copyright Sam Cullman

For decades, Mark Landis donated art to museums and galleries across the US. He was feted as a wealthy collector but the pictures were fakes that he had created himself. He was never prosecuted though - he didn't take payment so hadn't broken any law.

"It obviously isn't a crime to give a picture to a museum, and they treated me like royalty. One thing led to another, and I kept doing it for 30 years," says Mark Landis, one of the most prolific art forgers in US history.

"Have you ever been treated like royalty? Let me tell you, it's pretty good."

Landis's career as an art forger began in the mid-1980s, when he gave some pictures to a California museum, saying they were by the American 20th Century artist Maynard Dixon.

"It was an impulse to impress my mother. I always admired the rich collectors on TV giving away pictures to museums.

"I put Maynard Dixon's name on them because that's what the museums wanted," he says. "He was a cowboy artist, so I went to the library and checked out some books of photographs of American Indians, and copied a bunch of them.

"I knew the museums wanted cowboy pictures, so that's what I did."

Image copyright Mark Landis Image caption A Mark Landis copy of a watercolour by Paul Signac...

Image copyright The State Hermitage Museum St Petersburg Image caption ...and Signac's original work

As a teenager Landis had suffered a nervous breakdown following the death of his father, and was diagnosed with schizophrenia. Art therapy revealed his talent for copying, and he was able to turn out fakes at astonishing speed.

"I know everybody's heard about forgers that do all these complicated things with chemicals and what-have-you," he says. "I don't have that kind of patience. I buy my supplies at Walmart or Woolworth - discount stores - and then I do it in an hour or two at most.

"If I can't get something done by the time a movie's over on TV, I'll give up on it."

Posing as a wealthy benefactor, Landis donated counterfeits to dozens of respected institutions across the US until, in 2008, he walked into the Oklahoma City Museum. Matt Leininger was the museum's registrar, tasked with looking after new works.

"We just thought Landis was a really eccentric art collector," Leininger says. "The first piece he gave us, he actually hand-delivered - a watercolour by Louis Valtat.

"We framed the Valtat and put it on display next to a Renoir in our gallery, not knowing what we had just hung was a fake."

Landis continued sending forgeries to museums, and might never have been rumbled had he not offered copies of the same works to different galleries.

Image copyright Getty Images Image caption Matt Leininger (l) with Mark Landis, 2014

"We received an envelope in the mail which had five additional works in," says Leininger. They appeared to be paintings by the French 19th Century artists, Paul Signac and Stanislas Lepine.

What curator or director wants to admit they accepted fakes into a museum? Matt Leininger, Curator, Oklahoma City Museum

"I did some research on the Signac, and it showed up in a press release by the Savannah College of Art and Design under the same credit line - Mark Landis. I didn't think too much about it until I looked up the Lepine, and it showed up in a press release at the Saint Louis University of Modern Art - with the same credit line. That raised a red flag.

"I sent a message out, and within the first hour, between phone calls and emails I had 20 institutions call me and ask who this guy was and what was going on."

Leininger says Landis did a good job on his forgeries - but they didn't stand up to close scrutiny. One offering was a chalk drawing supposedly 300-400 years old. Leininger peeled back the brittle-looking mount board on the picture, expecting it to fall apart.

"It didn't, and when I peeled it back it was stark white," he says. "And it smelled like stale coffee. So he was using coffee to distress things to give them age."

The ease with which a simple inspection revealed the deception begs the question why so many institutions were so easily fooled.

"Landis would do his homework. He knew what museums collected. He was pretty sure they were going to be accepted because it would have fit their collection."

Image copyright Sam Cullman Image caption Mark Landis showing off some of his work in the documentary Art and Craft which told his story

The way Landis presented himself - and his donations - was also very convincing. "He said everything an art museum would want to hear," says Leininger. He had a "back story about how he had this art collection and supposedly family wealth, promising money for endowments".

Leininger sought advice from a former FBI agent who specialised in art crime. But because no money had changed hands for the forgeries, Landis had not broken the law. The burden of due diligence fell on the institutions who accepted his donations and if they displayed his fakes in their collection, that was their problem.

Landis had embarrassed dozens of galleries with his deception, and Leininger believes that some museums knew Landis was a fraud but kept quiet to save face.

"What curator or director wants to admit they accepted fakes into a museum?" asks Leininger. "Museums don't want to make that stuff public."

Landis meanwhile acknowledges his deceit, but says he doesn't feel bad about it.

"I'm like Pinocchio," he says. "You let your conscience be your guide. If something's really wrong, you kind of know. I wasn't worried about being prosecuted."

He continued to produce forged works, even after he had been exposed, and carried on donating to unwitting galleries. Indeed, his output increased after his mother's death in 2010.

Two years later, the University of Cincinnati put on an exhibition of Landis's counterfeit works. It was curated by Leininger, and opened - deliberately - on April Fool's Day. Landis was the guest of honour.

"I was really nervous before the show because I didn't know what to expect. But then when I got there everything was really nice. So I was pleasantly surprised," he says.

Landis and Leininger met at the exhibition, where the forger apologised for any problems he had caused. But was Landis embarrassed by what he had done now he was confronted with a room full of his own forgeries?

"Not really - except a lot of them were really bad," he says. "That's why I didn't want to look at them."

Mark Landis and Matt Leininger spoke to Outlook on the BBC World Service. Listen again on iPlayer or get the Outlook podcast.

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