The Bomb That Changed My Life
My wife worked in the city for one of the big banks.  A chap who worked there was in a similar situation.  He missed the train that had the bombers on board, but he decided to grab a bus to work instead.  This also had one of the bombers upstairs which moments later detonated killing most of the people on the bus.  
What made it even worse is that everyone who died that day was taken to a makeshift morgue on Moorgate which is overlooked by the people who worked in his team.  A really shocking day.