Eyewitness: "The train had just left King's Cross. Within three or four minutes there was a massive bang, the train lights went out and there was a lot of smoke and glass smashing," London worker Fiona Trueman, (26) said.
"There was four or five seconds and then everyone was going "oh, my God, we can't breathe".
"What was running round in my mind was 'am I dreaming?' I was in the second carriage.
"There was screaming and coughing with the smoke and no one could breathe. It was pitch black.
"Everyone was screaming to break the windows. No one was telling us anything, there was no contact from the driver - I don't even know if he made it.
"I can't really remember what the impact was like. We were all standing and the train was pretty crowded.
"Some people were saying 'everyone be calm, don't panic'. The screams from the carriage in front of us were terrible.
"We were in there for about half-an-hour. Lots of people were crying, trying to make conversation.
"Messages started coming down the line that they were unloading people from the train. London Underground and the police started letting everyone off from the back of the train and we had to walk along the tracks for 15 minutes.
"The really injured people were being brought through the crowds. We were evacuated from the site on double-decker buses. I think we knew it was a bomb because we could not see any flames. I thought we weren't going to get out of there."