The London Bombing, also known as 7/7 bombings, is about a series of three explosions that occurred on trains a little before 9 am and a fourth on a bus that occurred at around 9:45 am on 7/7/2005.  The explosions killed over 50 people and injured around 700 others.  They also severely affected transportation and the telecommunication infrastructure (due to access and security issues.)

The three train explosions occurred underground and within a minute of each other.   The initial assessment was that the explosions were a result of a power surge.  A diverted bus with some who were evacuated from the trains was traveling through tavistock when it too exploded.  The roof and the back end of the bus were blown away.  The Sun newspaper reported that witnesses saw a man exploding in the bus.

Sometimes initial assessments are correct. 

Explosions could be a result of ball lightning in the train tunnel which would cause a power surge.  Also the two witnesses did not say they saw a suicide bomber blow up, they said they say a person blow up.  That could have been a result of spontaneous human combustion which is also associated with ball lightning.