The steel door to the adit is now welded shut. But go up on the mountain top, past the entry for the T.S. Rees quarry, skirt around the side of the steel gantry and there is a hole (maybe 6-8 feet diameter) with a rotting tree stump maybe 6 feet down, to which is attached a ropey rope. Its a steep scramble down.
Not sure why the steel door was blocked, having been open for so many years. Possibly due to it being increasingly visited by poorly equipped idiots (at least one of whom put a video of their antics on YouTube) - I've found people exploring with nothing more than an iphone torch, pretty frightening considering the number of vertical shafts in the place which end either on unyielding surfaces, or in vertical sided pits of water.