Married father-of-six Michael Adebolajo, 29, had a Christian upbringing and his parents had taken him to church every Sunday.
Growing up in Romford, the "vast majority" of his friends were white British and one, Kirk Redpath, joined the Army and was later killed in Iraq.
"I hold Tony Blair responsible for his death," Adebolajo has said.
He converted to Islam in his first year at Greenwich University in 2002 or 2003.
He later took the name Mujahid, which means fighter. "I'm a soldier of Allah and I understand that some people might not recognise this because we do not wear fatigues and we do not go to the Brecon Beacons and train and this sort of thing," he said.
"But we are still soldiers in the sight of Allah," he said at his trial for the murder of Lee Rigby.
Defending the soldier's killing, he told the Old Bailey: "We planned a military attack which obviously involved, sadly - it's not something enjoyable - the death of a soldier."
Prior to Fusilier Rigby's brutal killing on the 22nd May, it appears that Adebolajo became increasingly radicalised.
He had attended demonstrations in response to what he saw as the persecution of fellow Muslims "in the hope it might make a difference."
"I was somewhat naive," he said in court.
He also described how at one demonstration he was arrested and sent to prison. He said that in his cell he realised the demonstrations were "impotent rage".
In 2010, Adebolajo visited Kenya and is believed to have been preparing to train and fight with the al-Qaeda-linked militants in Somalia.
According to intelligence files seen by ITV News, he travelled to the country's coast and met a group under the surveillance of anti-terrorism police.
It is claimed they contacted a radical cleric for help to get to Somalia. The cleric told ITV News Africa Correspondent Rohit Kachroo: "Michael was a very nice young man - a man of strong character and if you look at him you believed in his cause.
"They were to join their fellow Mujahideens [Muslims who proclaim themselves warriors for their faith] in Somalia and to assist, put a stop to the oppression many of the Muslims in Somalia are going through."
The group was later arrested in Lamu as they allegedly waited for a boat to Somalia.
One officer, recalling Adebolajo's anger at the time, said: "The British man said he's just a tourist, he's got the right to be on this island and no one can arrest him.
"But we had to arrest him. That was the order. He was very angry.”
In footage filmed in a Kenyan court, Adebolajo claimed that he and other suspects were innocent and had been subjected to mistreatment.
Adebolajo was later deported. His lawyer at the time, Wycliffe Makasembo, said: "The British Commissioner gave Michael a clean bill of health, meaning that he had no connection with any criminal organisation - al-Qaeda or al-Shabaab."
A letter seen by ITV News outlined claims from Michael Adebolajo's family that British security services wanted to recruit Michael Adebolajo as an agent.
Written in April 2012, it also alleges that he tortured when he was arrested and detained by anti-terror police in Kenya in 2010.
A friend that went to Islamist protests with him said those approaches became too much.
Abu Baraa said: "I think he felt that MI5 were destroying his life, that his life as he knew it was over, that he had no control over his own future and I think he wanted to take that control into his own hands rather than leaving it up to M15."
Three years later, Adebolajo would claim that Lee Rigby's murder was in response to "those responsible for sending British troops to kill Muslims".
Michael Adebowale was stabbed in a gangland attack when he was 16. He was later jailed for drug offences.
Richard Taylor OBE, father of murdered schoolboy Damilola Taylor, mentored Adebowale as a young boy and he was radicalised in jail.
He told ITV News: "I thought his going to prison would have reformed him and he'd come back and get back into the community with positive behaviour.
"Something must have gone wrong in prison, they must have indoctrinated him in the wrong way", he added.
Adebowale did not offer evidence at the trial but shares Adebolajo's belief that he is a soldier of Allah, his defending counsel, Abbas Lakha QC, told the Old Bailey.
Abbas Lakha QC said both men killed the soldier "as soldiers of Islam - this was a military operation they planned together and their target in that operation was a British soldier, and only a British soldier, no-one else."
Referring to both men with their adopted Islamic names, Adebolajo as Mujahid Abu Hamza and Adebowale as Ismail Ibn Abdullah, Mr Lakha went on: "On behalf of the second defendant (Adebowale), I did not challenge Mr Abu Hamza's evidence.
"What that means is Ismail agrees with what Mr Abu Hamza said about the reasons for the killing of Lee Rigby and they were acting together in that way and for those reasons. That is his case."
Very little is known about how the two men’s paths crossed, leading to them carrying out their brutal attack.
They were both found guilty of Lee Rigby’s murder and will be sentenced in January.