Taken from
http://uk.news.yahoo.com/bestival-bu...103624064.html
"Mr Hannell denied "overloading" was a factor - pointing out that one crew seat, one driver seat and 51 passenger seats added up to 53."
I doubt if one extra person would cause a coach to be overloaded enough to crash. If they were not in a (belted) seat, eg sitting on the floor, then they might suffer more injuries during the crash. Sudden driver illness or, a catastrophic vehicle failure are, to my mind (usual caveat about pure speculation) the more likely causes. The medical eperts will detect one of them and the vehicle experts, the other.
In the meantime, best wishes to
all of those people whose lives have been affected, by this tragic event.