In reply to tony:
I'm surprised that no one has commented on the reported response from one of the officers in charge when asked by one of the bereaved parents why the exercise was not postponed - "too much paperwork". An astonishingly stupid and callous remark.
Not sure exactly what the officer was supposed to have said.
However, there is no way the selection process at that stage could be postponed, or even the test conditions changed.
Only thing that could be done, was for individuals to be removed when they showed any signs of a life threatening/changing condition or severe injury, etc.
I imagine the permanent staff involved are pretty clued up on all sorts of medical matters, but at the end of the day, they're probably SAS themselves and therefore know how much it means to finish the march and that makes them quite likely to let people continue when perhaps they shouldn't.
The only real answer is to have Doctors who can over rule the permanent staff at each check point and perhaps have some sort of 'body function' monitoring device sending out live data.