A Druids altar at Ludchurch?

I came across the following account regarding Ludchurch in an old book which is probably around 120 years old, in the account there is a mention of a Druids altar and also an outlet connecting to the blocked cave at the southern end of Ludchurch. Although I have made a cursory search for this outlet below Castle Rocks, close to the Dane, I have so far been unable to find it. The account from the book is as follows:-

Ludchurch, which is stuated in the centre of the “Backforest” on Swythamley Moors, and which in ancient days embodied part of the forest of Lak or Leek, is a curious ravine or chasm forming a romantic winding glen about 200 yards long, varying in width, and from 80 to 100 feet deep.

The mossened sides have a dark greeny-grey appearance, and in its crannied walls of rock grow varied ferns and such like plants that delight in damp and shade; a darksome light haunts the place by reason of the overhanging oaks and mountain ash which form a sort of canopy, with here and there a peep of blue sky overhead. A little distance inwards, down some rough hewn steps, in a rocky niche is the figure of a “woman in white” placed there many years ago to commemorate the old legend of the meetings held in the comparatively  unexplored cave at the further entrance, which extends a considerable distance, with a supposed outlet not far from the River Dane, and where the remains of a sort of Druidical altar is still to be found. It was here in a fight with some soldiers sent to repress the Ludite gatherings that the daughter of Lud, the priest, met her death.

Romance has environed with its halo other romantic tales of this remarkable place, but although the legends and traditionary stories clustering around folk-lore oftentimes rest upon a shadowy foundation, they yet serve to amuse and focus interest upon such spots as this.

Ludchurch, with its gloomy aspect, is not a place to induce a traveller to linger, its beauty is of the savage order, the lineaments cold and harsh, and besides “the weird spell of silence most oppressive reigns,” so that in quitting its precincts and emerging to light and freedom a feeling of relief steals over the mind of the explorer.