There are at least two images of the arch in existence, both of which can be found in Gabb*. Gabb (p.28) notes that the arch fell in a storm in 1910 - possibly the late December storm that also hit North Devon*.

The co-incidence of the rock-arch with rumours of a local church set up by Illtud, and the closeness of a cave linked with the burial of a stranger (Note), seems almost too good to pass over. One might argue counter to this that a rock-arch isn't a free-floating levitation, however, if one reads the description closely it is not clear that the stone was free-floating when in situ. The description notes that the minor king...

...has formed a curve around the altar and he has held the twig by both hands from both sides and he has drawn it to himself...

– which isn't quite the same thing as forming a curve and then passing it around the altar. That said, one would have to go to some lengths to get a withy around the arch as shown in this 1805 print. Looking at the print it appears that the arch owned its existance to a hard and blocky layer of rock which dived into the beach at this point. The remains of this layer can be seen in the current limb and mid-way up the arch on the print. This layer was obviously of sufficient interest to the quarrymen locally for the cliffs at this point to be more deeply quarried than the cliffs to either side (Photo). It seems possible that the arch developed with a 'lintel' at this point, though this is very speculative.

Alternatively, the description may refer to another local rock-arch which was (is?) on the middle "Mumble", one "Mumble" from Bob's Cave. You can see it on a postcard here.