Seymour Hersh’s first big scoop—before the revelations about an American massacre in the Vietnamese village of My Lai started his great award-winning streak—was about the US government’s secret programme to develop chemical and biological weapons. Deducing that the people most likely to talk to him were retired, he read back issues of army newspapers, searching for short stories about retirement parties that would often mention where the general in question was retiring to.

“I got a list of names and addresses, made some calls, and took off, full of my customary enthusiasm,” Hersh recounts in his new memoir, Reporter. He spent two months on the road, visiting retirees and piecing together an incredible story. What he uncovered was undeniable. There were documents, there was evidence and there were people on the record.

Hersh worked for the Associated Press and he duly filed 15,000 words split into five parts, hoping to make a splash. An editor put it in a drawer. Eventually, just over 1,000 words was run, complete with a re-written introduction that claimed the Soviet programme was just as bad. Undeterred, Hersh found another outlet and over time, despite the denials from the Pentagon, it became accepted that he’d been right.

This pattern—of getting a tip-off from a source, then digging deeply to find the proof before struggling to find an established outlet willing to print the story—is one that has followed Hersh throughout his career. It has established him as one of America’s finest investigative journalists, a reporter whose work has to be read, whether it is about the Watergate cover-up that led to the impeachment of Richard Nixon or the revelations of US torture in Iraq’s Abu Ghraib prison.

But for the man himself there was another, perhaps more important, lesson: namely that the US government lies. Robert McNamara, the US secretary of defence during the early stages of the Vietnam War was a “psychotic liar,” Hersh told me when we met in London in June. Henry Kissinger was “the other great liar of our time.”

Rare is the senior US official who Hersh doesn’t believe is deceiving him, often with good reason. Throughout Reporter a host of presidents, secretaries of state and other assorted politicians, from Richard Nixon through to Barack Obama, are accused of dissembling. And if the US government is lying, that means their opponents may be telling the truth. “We were always told ‘if the Russians say it, it can’t be true,’ ‘if the North Vietnamese say it, it can’t be true,’” Hersh says. “I really learned not to believe that stuff.”

***

In 2003, in the early weeks of the Iraq war, Hersh made his first visit to Syria. In Damascus, he met with Bashar al-Assad, the first of several one-on-one interviews he would have with the Syrian president over the coming five years. In Reporter, Hersh’s descriptions of Assad are neutral to the point of kind. Assad is “tall, gangly.” Before giving Hersh his first answer Assad asks “shyly, if it was all right if he gave me a detailed answer”—Assad had once been told that his answers were too long. Three times, Hersh approvingly describes Assad as “secular,” as the Syrian president reiterates his support for America’s fight against al-Qaeda and the support he has given to the CIA. “Assad’s intelligence had been vital,” Hersh claims.

Assad tells Hersh about a “clumsy effort” by the CIA to recruit a Syrian intelligence source inside al-Qaeda, which leads to the source breaking off all contact. Assad “urged” Hersh not to write about it because “he hoped the Bush administration would come to realise that Syria, a secular nation, could be an asset in the War on Terror.”

During this period, Hersh also met Hassan Nasrallah, the leader of Hezbollah, a man he describes as “professional and affable” with an “ironic sense of humour.” American presidents, says Hersh, “were making a huge mistake in not dealing with both men,” though he admits that his editor at the New Yorker, David Remnick, was “far more sceptical than I was of the integrity of Assad and Nasrallah.”

Written seven years into the Syrian war, which has cost the lives of hundreds of thousands of civilians, Reporter contains no criticism of Assad—not once does Hersh reflect on whether his early impressions of the dictator were naive. In person, Hersh goes further. “I liked Assad,” he says. “I thought he improved a lot as I met him. He never did enough on human rights but he was moving.” Hersh cites the arrival of cash machines and the broadcast of a Turkish soap opera about an unmarried mother as evidence. “He was getting better. He was much more confident every year. You could speak out against him a little bit.”

That wasn’t the experience of those who protested against the Assad regime in the southern town of Deraa in March 2011. A group of boys had written graffiti in support of the Arab Spring. They were badly beaten up by Assad’s security forces, sparking protests which were brutally suppressed by the regime—the uprising had begun.

“No,” says Hersh. “I have a different view of the uprising. I haven’t written it, but I have a whole different view of that war. It flies in the face of what everybody else thinks.” Hersh’s version sounds an awful lot like Assad’s. The Syrian leader has always claimed that “terrorists” were behind the original protests—sometimes he has claimed it was al-Qaeda, at others he has suggested that the Israeli secret service, Mossad, and the CIA were involved. Hersh won’t say who he believes was responsible for the demonstrations, only that “sharp shooters” killed several of Assad’s security forces. “That’s a provocation.”

***

Hersh’s decades-long relationship with the New Yorker ended in 2012, when Remnick rejected a piece about the death of Osama bin Laden that went against the official government line. Instead, he turned to the London Review of Books, where he focused on Syria. Between 2013 and 2015 he wrote three long articles pouring scorn on the most widely known atrocities committed in the war: the chemical weapons attacks carried out by the Syrian government.

In one essay, Hersh claimed that the US government knew a jihadi opposition group, Jabhat al-Nusra, also had sarin, but downplayed this fact to justify a bombing campaign against the Assad regime. In another, he claimed the attack had been orchestrated by Turkey, working in conjunction with Jabhat al-Nusra, who hoped the attack would be blamed on the Syrian government.

The claims, if true, would be astonishing. The fact that the US government had a different view meant nothing to Hersh—they lie, remember. Nor did he seem to mind that the United Nations’ formal investigation, while barred from assigning blame, made it clear that only the Syrian government could have been responsible. (“If you think the UN is an objective place, I’ve got a bridge I want to sell you,” Hersh tells me.) Nor did he care that human rights groups such as Human Rights Watch disagreed with him (“Human Rights Watch do some great stuff. I think their stuff on Syria and Russia is nuts”). Nor was he persuaded by the widely respected independent analysts such as Dan Kaszeta and Eliot Higgins (Higgins is “a couch potato”).

But, strikingly, if he seemed to revel in the disapproval of western experts and governments, he didn’t mind at all that his work was widely praised by supporters of the Russian and Syrian regimes (“I think they should, why not? They [Syria] are denying it and the Russians are denying it”).

Unlike his investigations into America’s chemical and biological warfare programme in the 1960s, there were no witnesses, no documents and no damning evidence. Instead he had quotes from a handful of anonymous former US officials. To Hersh’s band of supporters, this didn’t matter. It was Sy Hersh, the guy who uncovered My Lai and won a Pulitzer. It must be true.

For the LRB, Hersh’s stories were becoming problematic. “Mary-Kay Wilmers (the LRB’s long-serving editor) got very nervous about my last story. She told me she didn’t want to be accused of being too pro-Russian and too pro-Syria. Obviously, they thought I was being too pro-Syria, a lot of people do.”

Wilmers was right to be nervous. The story she passed on, which was published in the German newspaper Die Welt, is the most controversial. In it, Hersh states that the most recent chemical weapons attack in Khan Sheikhoun was not, as the UN and the Organisation for the Prohibition of Chemical Weapons (OPCW) claimed, a sarin attack carried out by the Syrian government. It was, instead, a conventional bombing raid that happened to hit a warehouse of “fertilisers, disinfectants and other goods.” This caused “effects similar to those of sarin.”

Chemical weapons experts say this is impossible. Laboratory tests proved that sarin had indeed been used. Hersh disagrees. “Why am I doing this?” he asks at one point. “I don’t feel like explaining this,” he says later.

Hersh likes to portray himself as a principled reporter ploughing his lonely furrow. It doesn’t matter if others don’t believe him. “I’ll wait,” he says. But is this true? While many of his scoops were slammed by the US government, they were too persuasive to brush off, and were followed up by the rest of the media. His My Lai coverage crossed the Atlantic and was splashed on the front page of the Times. His Watergate stories were followed up in the Washington Post. The revelations about Abu Ghraib were aired on US television. They have become accepted truths—because they were actually true.

Today, his latest work leads the headlines on RT, the Kremlin-funded news channel that slavishly echoes the Russian government’s line on Syria (and, indeed, everything else). It is approvingly sprayed across social media by pro-Assad supporters.

In his defence Hersh likes to cite the work of Ted Postol, a professor of science, technology and national security policy at MIT. I point out that Postol has appeared on a podcast run by a Holocaust denier, where he spoke about how he relies for his work on Syria on a pro-Assad blogger, Maram Susli, who goes by the name Syrian Girl. Hersh gets angry. “He talked to her once on one thing,” he says, waving his arm in frustration. “My god, he talked to her once.” Postol’s work is often discussed on Infowars, the conspiracy theory channel run by Alex Jones—a man who once claimed the Sandy Hook school massacre, where 20 children under the age of eight were killed, was a hoax. “What’s Infowars?” Hersh asks. It’s run by Alex Jones. “Oh, he’s crazy. Alex Jones is a nut. I can’t be responsible for what he runs.”

Later that evening, I search “Infowars” + “Seymour Hersh.” It turns out Hersh should know what Infowars is. Up pops an interview he did with Jones on his show in December 2015.

***

Much of the criticism of Hersh hinges on the idea that something has changed, that the legendary investigative journalist of the 1960s and 1970s has turned into a conspiracy theorist who doesn’t care for facts. Others mutter unkindly about old age. A friend who has written about Syria for more than a decade referred to his recent work as a “twilight aberration.” Hersh would deny that, vociferously. “I have the same sources. I haven’t changed. I have people that see a lot of stuff. They talk to me… What can I tell you? I just operate at a different level.”

There is something else that hasn’t changed either—his cast-iron belief that the American government is lying. They were lying about the chemical and biological warfare programme. They were lying about Vietnam. They were lying about Abu Ghraib. And now, of course, they’re lying about Syria.

Yet after decades of exposing lies told by the American government, it is almost as if he has forgotten that other governments have their own reasons for being mendacious too. He seems to jump from the fact that America has denounced an atrocity to suspecting that it never happened. And when it comes to the regimes that America points the finger at—like Syria—Hersh’s scepticism, the inquisitiveness, the “why-are-these-lying-bastards-lying-to-me?” approach is entirely absent. Hersh doesn’t see it that way. “If you think that I’m going to throw away 45 years of my reputation for Bashar al-Assad.” He lets out a loud, mirthless laugh.

***

It’s evening by the time our conversation ends, but Hersh has one more appointment: an interview on RT. It’s a 30-minute special, just Hersh and the interviewer, whose line of questioning is at the more adulatory end of the spectrum.

In between explanations of his reporting, Hersh seeks to diminish his critics by claiming they are part of a “propaganda organisation.” In doing so, he repeats a lie created by pro-Assad propagandists to cast aspersions on his victims. “Too many times we’ve seen the same child in photographs year after year always covered in dust,” he says. He’s referring to an 11-year-old child, often called “CNN girl” by Assad’s online supporters. The closely cropped photos do indeed show the same girl covered in dust being carried by three different men.

This is proof, apparently, that the girl is an actor, used in videos and photographs staged by rebels to falsely show the barbarity of Assad’s bombing campaign. You would expect any reporter to verify such a claim before repeating it on television. Anyone with a computer would find that all three images were taken on the same day and show the girl being passed from one rescuer to another, and then on to her father. She is not an actor, she is a child who has survived a bombing and been turned into a propaganda tool for the dictator who tried to kill her.

“There’s been a lot of good reporting on it,” Hersh says. There has, but not the way he means. I email Hersh, showing him the evidence that he is mistaken. “If you take the time to look,” he writes, “you will find a plethora of the same allegation that I made.” He offers no evidence, just his word.