I am just wondering what decisions, or group decisions would make anyone else in a group liable in the event of an accident?
An accident is just that! How could the owner/s of an aircraft be liable?
No "decisions" are required. The law makes the owner liable, without fault on the owner's part.
So the odds of this scenario may be many millions to 1, but I have to accept that if it does occur I may be responsible, even though I did everything right and wasn't in the aircraft and able to influence the events immediately leading up to the incident. Doesn't really seem fair, does it?
I can't say I really disagree. The liability is often seen as a quid-pro-quo connected to the trespass/nuisance exemption just before it:
76. Liability of aircraft in respect of trespass, nuisance and surface damage. —
(1) No action shall lie in respect of trespass or in respect of nuisance, by reason only of the flight of an aircraft over any property at a height above the ground which, having regard to wind, weather and all the circumstances of the case is reasonable, or the ordinary incidents of such flight, so long as the provisions of any Air Navigation Order and of any orders under section 62 above have been duly complied with and there has been no breach of section 81 below.
So there ya go: You can annoy the hell out of people by buzzing around over their land to your heart's content with impunity, but if you drop onto their property you're responsible for any damage.