I am surprised that no one so far has mentioned two significant factors that may have a bearing on post accident procedures:
A. The loss of Crown Immunity
b. The Corporate Manslaughter and Corporate Homicide Act 2007
Investigation of any suspected cases under the latter are the responsibility of the police. Therefore it would seem appropriate for the civilian police to keep at least a watching brief on any investigation into a fatal accident or even assume a more active role in seeking to preserve evidence.
YS