This picture appears in the 1995 South Wales Argus publication "IMAGES OF NEWPORT".
The caption under it reads 'Pedestrians may safely pass over Caerleon Bridge after the opening of a footbridge alongside in 1968'. This is true, of course, but a closer look at the photo reveals that the footbridge is on the wrong side of the old bridge! Clearly it has been superimposed on an old photo.
Presumably the planners looked into the options of placing the footbridge upriver or downriver of the old stone bridge.

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Photo courtesy of The South Wales Argus.