Dozens have been killed and hundreds injured in a series of explosions on London's Underground trains.
I was in the second last carriage on a Piccadilly Line train. We had just left Kings Cross and had not gone very far, perhaps a minute.
Everything was normal. Suddenly there was a massive bang, the train jolted. There was immediately smoke everywhere and it was hot and everybody panicked. People started screaming and crying.
But not long after people were panicking, there were some cool-headed people who were saying "calm down, everybody calm down, don't worry it will be OK"
All the carriages were absolutely packed. Everyone crouched down as well as they could on the floor.
A couple of men started trying to open the train doors a little but some people were unsure as to whether the smoke was from the carriage or was coming from outside. They managed to get the doors open about five or 10 inches. Slowly the smoke started to filter out.
But then it sounded like another train had come up behind us and the carriage filled with smoke again and people became really, really frightened.
People were crying and then people started talking and shouting between the carriages. They kept saying there were people leaving the carriage behind us. They were saying they had broken a window and they started smashing a window in our carriages
We were there about 20 minutes before engineers freed us. There were absolutely no announcements during this time.
We were led out down another tunnel back to the station, which was then evacuated.
It was very scary while we were stuck on the train. Very silent and we were thinking we were not going to get out. People thought they were just going to suffocate.