In mid-September, 2016, Laura Lozanski received an e-mail from a British documentary filmmaker named Rob Moore, asking if she would be willing to do an in-person interview with him on the health risks of asbestos.

The former nurse and occupational health and safety officer for the Canadian Association of University Teachers had no reason to be suspicious. He came to her Ottawa office on Sept. 23, where he interviewed her for about an hour. He seemed friendly, sympathetic and concerned about the issue. He said he had been doing documentary films on the impact of asbestos in places like Thailand and through South Asia.

"He was making these films about these poor children who were exposed to asbestos and was looking for support for that."

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Ms. Lozanski had spent more than a decade working to educate people on the dangers of asbestos exposures, and advocating for a ban. She shared information that was in the public realm, about where asbestos currently exists in Canada, and that she and many others were hoping to see the federal government announce a ban on asbestos. (Canada had long supported the asbestos industry, a position out of step with most developed nations; in December, after mounting pressure from medical experts, scientists, labour unions and affected family members, the government said it will introduce a ban in 2018.)

Ms. Lozanski introduced him to at least half a dozen other Canadian contacts in the field.

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She didn't hear back from him after that. In early December, she learned of an espionage case in Britain's High Court, over someone posing as an investigative journalist and filmmaker who had infiltrated the global ban-asbestos movement over a four-year period. After the prohibition on publishing his identity was lifted and she saw a photo of him posted on a blog, she realized he was the same person she'd met.

"Betrayed," is how she now feels, "because there's a lot of trust in this.

"That someone would go to these lengths, to not only use me to talk to me and get information, but that I willingly shared e-mail introductions to my other network colleagues. It's a really reprehensible thing," Ms. Lozanski continued.

Many of those advocating for asbestos bans have long faced intimidation from asbestos-industry interests, which have also disputed overwhelming evidence of the health risks of exposure to the mineral. The World Health Organization has pegged the number of deaths from asbestos-related lung cancer, mesothelioma and asbestosis from occupational exposures at 107,000, as of 2004, globally.

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The case now before the High Court involves a corporate intelligence firm called K2 Intelligence. Over four years, the court heard, a spy working for the company posed as a documentary filmmaker to gain access to people in the global anti-asbestos movement, where he obtained sensitive information about campaigning strategy, funding, key figures and plans.

K2 then allegedly passed along information to its client, thought to be an entity with interests in the asbestos industry, which has not yet been publicly named.

His methods and the scope of the operation came to light after an October injunction ordered him to disclose to claimants copies of all information he had obtained in the four-year period. The subsequent disclosure to date amounts to about 35,000 documents, e-mails, texts and audio files. About 650 of those were sent to K2, according to a witness statement submitted by the claimants' solicitor, Richard Meeran. The documents also revealed he had received more than £460,000 from K2 in salary and expenses between 2012 and 2016.

K2 Intelligence, whose co-founders are Jules Kroll, a well-known leader in the corporate investigations field, and his son, CEO Jeremy Kroll, is a global firm with headquarters in New York. The company's services include "providing intelligence and addressing risk across the strategic, operational and reputational landscape," its website says. Its clients include businesses, governments and high net-worth individuals.

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The three claimants in the case include Laurie Kazan-Allen, founder of the International Ban Asbestos Secretariat. They are alleging breach of confidence, misuse of private information and breach of the British Data Protection Act. They are seeking compensation for their distress.

The first defendant in the case was listed in the court documents as "DNT" because of an anonymity order. That publication ban has been lifted, and the defendant's name is Robert (Rob) Moore, two lawyers for the claimants said, though the High Court did not respond to a request for confirmation by the time of publication.

Asbestos has been banned in more than 50 countries around the world, including Britain and all of the European Union. The known carcinogen is still being used elsewhere. Key producers of chrysotile asbestos are Russia, China, Kazakhstan and Brazil, while importers include Thailand and Vietnam.

Court documents paint a picture of Mr. Moore's alleged tactics. "I've been able to identify several news stories, angles, pegs and themes that would be of genuine interest to a documentary-maker/journalist, and I am confident I can enter this world relatively easily and with a high level of legitimacy and credibility," reads a disclosure of a "Phase One" report to K2, adding that "the stronger my cover, the bolder I can be."

In one 2012 disclosure, according to a witness statement, Mr. Moore identifies key areas of focus – one of which was to learn of the ban-asbestos movement's plans for Canada, along with plans for Thailand and India.

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"He obviously was very credible, very persuasive, very charming. He really got people to open up and to trust him," said Guy Vassall-Adams QC, a barrister who represents the claimants, in an interview. His modus operandi, he said, was to befriend one person and ask for introductions to others. "From a single individual who he targeted, he was able to get access, over time, to really the whole of the ban-asbestos movement – not only the key people in Britain, the States, Canada, but also in Thailand, Bangladesh, India, Vietnam."

The resulting reports sent to K2, Mr. Vassall-Adams said, "are of extremely high-quality intelligence. They are very, very detailed, they are written as you would expect of a really thorough investigative reporter to write up, really careful, well researched."

Among his activities were attending global conferences, and gaining intelligence on the activities of various United Nations agencies, including the World Health Organization, according to court documents. At times, he said he was raising money for a charity.

Lawyers representing K2 and Mr. Moore didn't respond to requests for comment. K2 global chief marketing officer Paula Zirinsky told The Globe and Mail the company doesn't "publicly discuss matters that we work on. But we'll vigorously defend ourselves from the allegations in the appropriate forum." When asked follow-up questions, she didn't elaborate.

When contacted by e-mail, Mr. Moore said it would be premature to comment on the case.

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Ms. Lozanski is not the only Canadian he contacted. A filmmaker named Rob Moore also interviewed Paul Demers, a scientist at Cancer Care Ontario, by phone in September, and Bob Blakely, a lawyer and operating officer for Canada's Building Trades Unions, who he met at his Ottawa office for an interview.They were both asked about asbestos exposures and diseases, and for more contacts in the area.

"He said he was a British journalist and documentary filmmaker. He was charming … he had a professional demeanour," Mr. Blakely said. "When I reflect on it, clearly what he was doing was amassing information … he was intel-gathering."

In Washington, Linda Reinstein, a mesothelioma widow and co-founder of the Asbestos Disease Awareness Organization, allowed Mr. Moore to attend her annual conferences in 2013 and 2015. She remembers him as disruptive, constantly taking pictures of the slide-show presentations and conducting numerous interviews. The organization even paid thousands of dollars for his travel and conference expenses. In 2015, he was a conference presenter and screened a short video he had produced.

"This was a betrayal of my work, our voices and the time so many volunteers spent to make our conference impactful," she said. "It's a tragedy to feel that your trust has been broken."

The case has wider implications, Mr. Vassall-Adams said. "Journalistic cover, you can see why it works, as a good device by which you go in and get information from other people, get them to open up and trust you," he said.

"And it is very contrary to the public interest, because it destroys confidence in journalists. It does a terrible disservice to genuine journalists. Because, in the ban-asbestos movement, who's going to want to talk to a journalist now, unless it's someone they already have a rapport with? … Peoples' trust has been completely undermined."