It was the first time I'd ever been to the Pre-65 and that was the only thing that marred what was otherwise a great Trial.
It's not such a problem at the Six-days as it's well publicised that spectators bikes are not permitted on any part of the course and on the whole, people respect that (there is the odd moron who thinks they know better i.e. Father & son, Ben Nevis, Saturday.)
I could find nothing in the Pre-65 programme saying anything about spectators bikes staying off the course, although to me it would only be common sense.
It's something that needs to be addressed though, not only from an insurance point of view, but for ensuring the continuation and success of both events.