I have a bit of a puzzler with RIDDOR reporting. Using the guidance L73 it states in Para 45 that
“Any injury to a person who is not at work must be reported if it:
a. Results from an accident arising out of or in connection with work and
b. Results in them being taken from the premises where the accident occurred to a hospital

What happens if a member of the public, walking through a nature reserve tries to climb a vertical sand dune and injuries themselves?

Does it get reported or is it there own stupid fault?

Results from an accident arising out of or in connection with work
and
Results in them being taken from the premises where the accident occurred to a hospital

What happens if a member of the public, walking through a nature reserve tries to climb a vertical sand dune and injuries themselves?

How does your question relate to the scenario- from what I can see it is not work related and they were not taken to hospital.

Firstly, who may be to blame is not relevant as to whether an incident is reportable or not.

It is the "arising out of or in connection with work" that is the key test.

If you are satisifed from your investigation that the incident was not caused by anything arising out of or in connection with the work of the Nature Reserve then it is not reportable under RIDDOR.

So for example if this vertical sand bank were a temporary situation during ground works being carried out then it would likely be considered as arising...... If it is a natural bank then how can it arise from work....?

I would not have reported it if it was a fall from a natural bank. Some no doubt may argue that the work of a nature reserve is to preserve nature and all its hazards but I really cannot see that RIDDOR was ever designed to capture such incidents.

p48