And as I said, it is not whether the kit did have a contributory cause, it is whether that was a reasonably forseeable consequence of that instruction, that could lead to a negligence claim. So I doubt that any liability could ever attach, because hundreds of thousands wear such garments every week on the hills without the bizarre happening.
As regards reasonable forseeability:
The clause in our rules stating that field size has to be such that there is no forseable risk of accidents in crowded areas - clearly does create a liability ( solicitors have pointed at - but FRA not listening) since the risk of a group of any size moving over rocks is forseeable. So you cannot run a langdale or borrowdale with that clause in: both of which have a first trip up mile whilst runners are tightly packed, cannot see, and trampling is also possible. Those accidents in the first mile are forseeable hindsight and foresight.
Because of that inane piece of drafting the RO cannot even do the responsible thing of warning the runners of the clearly forseeable risk in the first mile, (the correct control measure) because in doing that he is owning up to a risk the rules say he should not have - owning up his course is not compliant and so is rulebreaking, putting a further target on his back, in event of problems!