Tre ball joint would give play, which the driver would have to centre with the steering wheel. Or the car will vear off.
This means ball joint play affecting the toe setting would give equal wear on both front tyres. So not caused by a tor error.
Which means.... Camber. Either poor set up or a fault causing excess camber.
Runs fairly true, maybe a slight lean the the left, but narrow country road camber could account for that. 
Depends on the operator. Sometimes they add a bit of camber to the left side to counter the road crown. Which might explain it. Others prefer to reduce caster on the drivers side for similar reasons. I hate both these options personally as the car never runs true, even on the rare occasions that it actually runs on a flat piece of road.
Further, as the tyres then wear, oddly in your case, that can play havoc as well, and potentially cause a pull in its own right, as one tyre is then "geared" (like a cone) and wants to pull, while the other doesn't.
End of the day, ideally, you want the inner edge wear to be more than outside, BUT to be within limits by the time the tyre is worn out. ie, if the inner edge wear finishes the tyre with useable tread left in the centre then the camber is excessive for your driving as your not wanging round corners like the set up operator thinks you should be.... Or he's just made a bollards of it.
Basically, "some" inner edge wear should be evident by the time the tyre is shot. So it might be that the other more evenly worn side is too upright. (This doesn't apply to more "progressive" drivers as they'll wear both edges, leaving ALOT of centre tread still to use, although still want slightly more inner edge wear than the outside)
Author
Topic: Runway Enduros (Read 4598 times)