Hi there i have been in most of the adits in cwm bychan and there is a lot 12 plus and i think this one is a trial ,it comes to a end just after it turns left,the first one you come to after leaving the car park at nantmor is very interesting and further up the valley on the right there is an adit that goes about 100yds and looks to be very old,high on the hill side on the rihgt hand side of the left valley if that makes sence is a nother adit wich looks even older,hope this helps. dave;D