The reporter from the Washington Post who co-wrote the story revealing the identity of 'Jihadi John' said, on 26 February, the "public had a right to know" the killer's name.

Adam Goldman, who co-wrote the Washington Post article with Souad Mekhennet, reported that the man who has featured in several Islamic State beheading videos is Mohammed Emwazi, a Briton from a middle class family who grew up in London and graduated from college with a degree in computer programming.

The Washington Post said Emwazi was believed to have travelled to Syria around 2012 and to have later joined Islamic State.

The paper also said Emwazi had been born in Kuwait, was raised in a middle-class neighbourhood in London and occasionally prayed at a mosque in Greenwich, south-east London.

In an interview at the offices of the Washington Post, Goldman described the journalistic process that led up to him writing the article.

"The name was clear to US intelligence agencies and British authorities by September 2014," he said.

"So only weeks after they had the name. It's widely known in the intelligence communities. So I was assembling bits and pieces along the way. And then we also relied on what we knew from the video, and what we knew from hostages who had been with John and what they knew about John himself. We assembled those pieces and eventually they came up with a first name and then we learned a last name. It came to a head these last couple of weeks. And we sent Souad, who wrote the story with me, to London and she started knocking on doors. And we found his close friends who talked to us. So we had the name before we reached the friends. And they just added confirmation of what we already knew and people we had already talked to here."

In videos released by Islamic State (Isis), the masked, black-clad militant brandishing a knife and speaking with an English accent appears to have carried out the beheadings of hostages including Americans and Britons.

During his interview, Goldman shared the behind-the-scenes thinking that resulted in the newspaper deciding to publish Emwazi's name.

"When James Comey, the director of the FBI, announced to the world in late September 2014 that they knew the identity of 'Jihadi John,' we weren't telling 'Jihadi John' anything he already didn't know, that US intelligence and British intelligence had determined who he was," he said.

"So that was really a non-factor. Some people have raised the idea, 'Well they are still holding a British hostage, John Cantley'. I would suggest that John Cantley is in the gravest danger. We didn't believe that telling 'Jihadi John' what he already knew from James Comey, the director of the FBI, altered the equation. Not only that, the story has enormous public interest. You're seeing that from the reaction of the story from around the globe. This individual is responsible for beheading multiple people. I felt the public had a right to know."

The Post quoted friends of Emwazi, who spoke on condition of anonymity; saying they thought he had started to become radicalised after a planned safari in Tanzania following his graduation from the University of Westminster in London.

They said Emwazi and two friends never made it to the safari. On landing in Dar es Salaam, in May 2009, they were detained by police and held overnight before eventually being deported.