Hi Tony
This is one of those incidents where you should rely on the Regulations not HSE's guidance.
Some on this site know that I am not a fan of HSE guidance on RIDDOR. I wasn't a fan of HSE's guidance on accident reporting BEFORE the first iteration of RIDDOR, even when I was employed by HSE! I am long enough in the tooth to remember Section 80 of the Factories Act 1961.
So, you agree that it will meet the severity threshold for an "Over 7 Day Injury" accident.
At this point you have to decide whether it was "work-related".
So, RIDDOR defines this:
“work-related accident” means an accident arising out of or in connection with work.
Separately, "work" is defined in Section 52 of the parent Act that RIDDOR was made under - HSWA:
52 Meaning of work and at work
(1) For the purposes of this Part—
(a) " work" means work as an employee or as a self-employed person;
(b) an employee is at work throughout the time when he is in the course of his employment, but not otherwise ; and
(c) a self-employed person is at work throughout such time as he devotes to work as a self- employed person;
and, subject to the following subsection, the expressions " work " and " at work", in whatever context, shall be construed accordingly.
So, you say that this person was already on site and on their way to a briefing about what was to be done on the day.
This is MUCH easier than some of those RIDDOR questions about somebody tripping over the pavement when off site when they might or might not be "at work".
Not least since I presume that this person would be getting paid [thence "in the course of his employment"] to walk across part of the site e.g. to get from welfare facilities to the locus of the site briefing.
WHATEVER the HSE guidance says (!) if all this is the case then I think the person was "at work". Ergo it was a "work-related" accident within the meaning of RIDDOR.
Remember that the HSE guidance takes account (and has for decades) that:
(a) successive Governments have been keen to reduce the burden on business of health and safety regulations - personally I don't think that submitting a RIDDOR is a particularly big burden!
(b) HSE has been responsible for collating accident data to be provided to Eurostat - anything that presents the UK in a good light in comparison with EU Member States is perceived as a good result! [Probably, one of various reasons why HSE has repeatedly rejected calls for most work-related transport accidents that would otherwise be reportable to NOT remain excepted from the scope of RIDDOR]
HSE probably don't actually want this to be reported as it's not good for the national statistics, but they draft the law. If they don't like it, they can ask the Minister to sign off on something different - that is on the assumption that there isn't so much flak during the necessary consultation for them to step back from something that would be clearly deregulatory.
As has been said countless times on these Forums, making a RIDDOR report is nothing to do with liability for an accident. A proper investigation will help determine whether there was anything reasonably practicable that might have been done to reduce the likelihood of tripping and/or mitigate the likely consequence - very likely NOT. How many of us have not tripped on a kerb at some point in our lives?!?!