One is a 90-year-old US army veteran turned academic, specialising in Victorian theatre; the other was a thirtysomething Chechen Isis member, sometimes known as “Akhmed the One-armed”.

But for the past three years, some branches of the US government seem to have had them confused. And David Mayer, emeritus professor of drama at Manchester University, believes this strange case of mistaken identity has meant interrupted work, lost post and at least one frustrating travel delay.

After serving in the US army as a second and first lieutenant in Korea, with FBI clearance to read “secret” and “top secret” classified documents, Mayer went on to a distinguished career in academia. He is the father of the journalist and Women’s Equality party founder Catherine Mayer.

His first inkling of a problem came two years ago, when he tried to buy a vintage theatre poster on eBay. The seller emailed him to say the package had been returned, with a message from US Customs stating that the “recipient name matches a denied party/entity that may not send or receive exports”.

Mayer was baffled. The image showed a man kneeling in the snow in front of his wife, outside a hospital, advertising a 19th-century domestic melodrama called The Power of Gold.

“It was one of those posters that told me many things about theatre at the time, but I can’t think of anything being less subversive,” he said.

He tried calling the US Postal Service, but got no answers, so turned to Google. He eventually discovered that a Chechen militant called Akhmed Chatayev had once gone by the alias David Mayer (among a sheaf of other false names and noms de guerre, including Akhmed the One-armed). The suspected mastermind of the 2016 Istanbul airport attack, Chatayev had been put on a US government sanction list the previous year.

As far as the professor of drama could work out, this move had also caused an academic living half a world away to be placed on some kind of secretive blacklist.

Akhmed Chatayev under arrest in 2011. Photograph: Rex

It’s hard to imagine a less likely case of confused identity or one that should be easier for authorities to clear up. The real David Mayer, who moved to Manchester after marrying a British woman, has had a long career as an academic and has lived at the same address for four decades, since the year the militant “David Mayer” was born in Chechnya. So he at first thought that getting himself off whatever list he had landed on might be bureaucratic but should not be impossible. More than two years later, he is despairing.

“I’m helpless,” he says. He has contacted the post office, a congressman back in the US and the embassy in London; after none had any success, he even employed a lawyer to chase up the case. “She looked into it, and charged me a lot of money, and nothing happened.”

He still can’t receive any post sent from the US, and while official letters and packages are returned to senders, he believes many personal letters have probably gone missing.

The block is affecting the work that still keeps him busy at 90. “I’m not receiving letters, not informed of conferences, and I publish books in America and essays, and this makes it hard trying to deal with editors.”

He worries about travel disruption too. When he tried to check in online during his last trip to America, Mayer got a message saying he was not eligible to travel. He went to the airport anyway, carrying his military documents from over half a century ago, and was eventually allowed to fly.

“I now keep my army discharge certificate with my passport, in case anyone queries my nationality, and that I was once many years ago a lieutenant in the US army,” he says.

Adding to his frustration, some branches of the US government are perfectly satisfied that he is a citizen without a terror record. “They had no trouble sending me tax notices, and I do get occasional post from the veterans association.”

The US embassy declined to comment on an individual case, citing privacy issues. Travellers who believed they had been unfairly profiled could, the embassy said, apply to the Traveler Redress Inquiry Program.

Mayer is starting to despair of ever getting off whatever list he is on – or even finding out what list it is – and wonders how many other people have also been trapped in Kafkaesque confusion.

“It just seems to me so clumsy, so thoughtless,” he says. “What I don’t know is how many other people are caught up in this. Imagine the disruption if he had been using a name like John Smith? It’s astonishing.”

For years, there have long been concerns that secret watchlists are both too sweeping and opaque, with little room for those named – even the US elite – to seek redress. Senator Ted Kennedy, brother of a US president, was astounded to find himself on a terror screening watchlist in 2003; the Republican congressman Tom McClintock was put on the most severe “no-fly” list soon after. He later said he had been confused with a member of the IRA.

Both were eventually cleared to fly again but David Mayer has not even managed to find, let alone get off, the list that is causing his problems. Not even Akhmed’s death has helped. The Chechen was killed in a police siege in Georgia a year ago, but he has apparently lived on in zombie form on some terror lists. A package addressed to Professor David Mayer was returned to sender just last month.