A4.
I've not had the full info on what happened yet but as a Tug driver myself i can only assume that the Sheers pins gave way on the towbar causing the A/C to veer off in a different direction to the tug.
This happens rarely and the last time i can recall it happening was to a friend of mine towing a 733 about 2 years ago!
If i find out anymore i will update the posts.
Matt.