ITV News has revealed two British men who were believed to be a part of a so-called Islamic State terror cell that detained and beheaded a series of hostages in Syria.
Alexe Kotey and Aine Davis became friends with notorious IS killer Mohammed Emwazi - known in the media as "Jihadi John" - during their time in London long before travelling to Syria.
After joining the militant group, the trio were known by their victims as "The Beatles" - with Kotey, Davis and Emwazi given the nicknames George, Ringo and John.
Here is what ITV News has discovered about the pair so far:
Alexe Kotey: 'The leader'
Described as leader of the British cell responsible for the beheadings of westerners such as Alan Henning and James Foley, Muslim convert Kotey, 31, was a key recruiter for the radical group and brought a number of Londoners into its membership - including Emwazi and Davis.
He was born a member of the Greek orthodox church but converted to Islam in his teens.
Kotey, Emwazi and Davis all attended the Al-Manaar mosque in west London's Ladbroke Grove, but were marginalised for extremist views - with elders claiming in 2011 that Kotey had attempted a "takeover" and demanded that British foreign policy be discussed at the pulpit.
It is also believed that Kotey had been a part of a 2009 pro-Palestine campaign led by former MP George Galloway, though Galloway told ITV News he had no memory of meeting him.
After being thrown out by his mosque, Kotey organised private meetings nearby to discuss the interpretation of Islam - several extremists in attendance would later go on to fight in Syria.
A community worker who chose to remain anonymous told ITV News around a dozen young men would attend the classes at the mosque, adding that the "vocal" Kotey "was the spokesman in that little group".
It is not known whether Kotey, thought to be a father of two, is still alive, though it has been reported he may have died in a summer offensive against IS forces.
'He was like a politician'
A west London associate of the pair told ITV News he was not surprised Kotey - known as "Big Sid" - had taken such an active role in recruiting for the terror group, claiming: "He always had a lot of currency and pulled a lot of people into his orbit."
"He would meet people in the social atmosphere of the mosque, they make friendships over innocuous things like football and the gym, and then [he would] suck them into [his] orbit," the other source added.
[He was] the lynchpin, the main recruiter person who sucked people into his orbit... The mosque did so much to keep these people at the fringes.
Kotey was also said to have a "vindictive streak", with the associate claiming he knew of a number of mosque committee members had their property vandalised after elders distanced themselves from him.
It was also claimed that his associates had confronted mosque management for having a dialogue with police, while some had "shouted down" the preacher when issues such as Palestine were raised.
Neighbours, however, described him as a quiet man who was dedicated to Queens Park Rangers football club.
In the wake of ITV News' investigation, Kotey's family said they were "deeply distressed" but admitted they had not seen him for a "number of years".
Aine Davis: 'Needed guidance'
Born in London and with roots to Gambia, Davis has been mentioned in British court cases in connection with terrorism.
His wife, Amal El-Wahabi, was jailed in 2014 for trying to arrange to smuggle 20,000 euro in cash to her husband in Syria.The trial heard how Davis had a controlling influence over his wife, with whom he has two children.
In November it was reported that Davis, a former drug dealer, had been held by authorities in Turkey.
'He needed a father figure'
In contrast with the picture painted of Kotey, his associate Aine Davis is described as a vulnerable man "in need of guidance".
The associate from west London told ITV News he was an "incredibly decent and hardworking chap" who "wanted to make something of his life", but added that he was "impressionable" and "someone who could be easily swayed and influenced".
He really needed guidance. He was really close to his mother, he needed a father figure and when he didn't get that it was easy for him to get in a gang or cult.
It is said that he would often be seen with the influential Kotey, despite knowing that he was a destructive influence.
The source said he knew of people who had tried to convince Davis to stop spending time with Kotey, but added that it was not enough to "get him out of it".
Davis' father told ITV News Davis was not in Emwazi's Syria-based terror cell, though one of his hostages is clear that he was.