" helmet could be proven to have prevented any injuries sustained."
.
And I think there's the rub in the whole helmet debate.
Whilst "common sense" would indicate that wearing a helmet should be safer, it seems the scientific evidence to this effect is not conclusive either way.
Personally after looking at a few articles, I think this is because the type of headgear we call a "cycle helmet", is really not up to the job (and in some cases can contribute to injuries). A helmet that was up to the job, would almost certainly be unacceptably heavy and hot for most cyclists, so we are left with the unfortunate position of helmets that can protect against some cycling impacts, but is of debatable use for many others.
Anyway I've strayed far too close to the helmet debate full stop... (probably due to the amount of ahem, "WD40", I've had this evening
[rather nice Belgian WD40
] )... and with the improved weather, helmet debating is now out of season!