One possible theme could be the co - existence of the ordinary and the extraordinary. The London bus is a very ordinary part of daily life in London, but when ghosts are introduced, it becomes something extraordinary.
I'm not entirely sure specifically about Aidan Chambers' 'Ghosts London Bus Story'. It could potentially be a fictional tale involving ghosts on a London bus. Maybe it's a story about strange encounters or apparitions witnessed on a bus journey in London within the context created by Chambers.
Jessica Chambers was a victim in this story. She was a young woman who unfortunately became the center of a very tragic and mysterious case when she was found burned in a vehicle.
To determine if the Chris Chambers story is true, you'd need to look at the evidence and the credibility of the storyteller. Sometimes, stories like this have elements of truth mixed with creativity.