I would say it is almost certainly a bridge and not a pipeline etc. Pipes or cables entering the sea are exposed to massive forces from the waves, so the engineers will usually look for a nice sandy cove where the pipe/cable will be protected by a sandy cover (like at Porthcurno). If that isn't available then the usual approach would be to dig a vertical shaft near the clifftop and then a horizontal tunnel into the sea below the level where wave action is a problem. It would make no sense to carry the cable/pipe on an exposed bridge and then down the side of an exposed rocky headland.
I would go with DavidG02's idea of it being tourist related. I cannot see much of a path on the seaward side, so my guess is the bridge may be the attraction itself (for tourists to stare down into the 'chasm' below), or else that the outcrop has some special meaning and standing on it formed part of a pilgrimage. (like this is where 'X' threw themselves to their death).
The stone walls at either end are partly what bridge engineers call abutments - providing foundations for the ends of the bridge and a safe flat surface for users to transition from the bridge to land. The walls also stop people falling over the edge!
In terms of the rocks, the 'layering' (stratification) of those in the foreground suggests (although not conclusively) they are sedimentary in origin, which might help pin the location down. Somewhere along the Jurassic Coast perhaps?
