The four men who carried out the 7 July bombings were young Muslim Britons who had led apparently ordinary lives. Their profiles are below.
Mohammad Sidique Khan, 30, Edgware Road bomber
A married father-of-one and teaching assistant, Mohammad Sidique Khan was the oldest of the bombers and is thought to have taken the lead role.
Raised in Beeston, Leeds, he was the youngest of six children born to Pakistani immigrants who had taken British citizenship.
Friends from his teenage years recall a highly Westernised young man who insisted on being called "Sid".
Khan was known to the MI5, but officers assigned to investigate him were diverted to another operation.
Following the attacks a video message recorded by Khan emerged in which he said he was a "soldier" at "war".
His bomb, detonated on a westbound Circle Line train, killed seven people.
Shehzad Tanweer, 22, Aldgate bomber
Shehzad Tanweer was born in Bradford but lived most of his life in the Beeston area of Leeds.
Neighbours described the sports science graduate as a "nice lad" who could "get on with anyone". Friends said he was very religious, but did not express an interest in politics.
In 2004 he travelled to the Pakistani city of Karachi along with Khan.
The two became known to the security services, but were on the periphery of other surveillance operations.
Tanweer detonated his bomb on the eastbound Circle line, killing seven others.
Jamaican-born British resident Germaine Lindsay spent his childhood in Huddersfield, West Yorkshire, not far from the other bombers' homes.
He converted to Islam in 2000, took the name Jamal and, at around the same time, started to associate with troublemakers.
At school he was disciplined for handing out leaflets in support of al-Qaeda.
In many ways Lindsay's life was unsettled, but in 2002 he married a white convert to Islam, with whom he had a young boy. A daughter was born after his death.
Lindsay carried out the most deadly of the bombings, killing 26 on the Piccadilly line train.
Hasib Mir Hussain, 18, Tavistock Square bomber
Teenager Hasib Hussain was known as a quiet student with few friends whose life attracted little outside attention during his early teens.
Hussain was a second generation British citizen whose parents were of Pakistani origin. He grew up in Holbeck, on the outskirts of Leeds, and was the youngest of four children. He was still living with his parents when he died.
While still at school, he went on the Hajj pilgrimage to Mecca.
His family said they were "devastated" to learn he was the bus bomber who claimed 13 lives on 7 July.