This is very, very sad....but it was a one in a million chance, even with the poor vis. I fly in that area all the time. I take trial lesson students over to Blithfield Reservoir, because it's five minutes fromTatenhill where we're based, it's very pretty, students can have a go at flying round the reservoir (nice beginner's challenge) and IT'S NOT AT ALL CROWDED most of the time. You can't prevent or legislate against one in a million chances!