I tend to look at these types of issue from a liability standpoint rather than a legislative one. In my view if your staff are representing the company during the events you put on, (eg the XYZ & Co football team), and/or if the events are compulsory (ie no opt out), then the company could be wholly or partly liable for any injuries sustained and the injuries could be regarded as industrial injuries, meaning the company has to pay out. In this case I would expect some degree of risk assessment to be done by the organisers to ensure that appropriate precautions are taken to minimise the risks. If the company is allowing staff time off to undertake an event voluntarily, (eg to run a local marathon as an individual and not representing the company), then the need for a risk assessment is negligible/non existent. I would also look at who is insuring the event, the company or a third party. If it was the company then I am sure the insurers would expect some sort of assessment to be done also. This is just my view, others may differ.

Not sure the enforcing authorities would be chomping at the bit but if you arranged the event and she injured herself in the process you may well be found neglegent and end up getting sued. The purpose of a risk assessment is to highlight the hazards and put controls in place to bring down the risk to an acceptable level. I would carry one out; A) to protect the participants B) protect the company from liability I certainly wouldn't let any legal requirement be the driving force.

In terms of your scenario being work related I think much would depend on whether or not your staff could have opted out of the event, whether or not it is compulsory and whether or not it is done in work time. Many factors come in to play. In my opinion the accident could in some circumstances be seen as arising out of, or is in connection with work and therefore it could be potentially reportable. As others have said the liability/civil issues are probably more to worry about. If your company is organising an event Lawyers/loss adjusters and the like would expect you to have provided the correct equipment, instruction and training etc and would probably hold your company liable for any/all damages. The risk assessment process would identify the hazards and enable you to establish suitable control measures. Other opinions may differ.