Well done again Gwynant.
The walkway was for the Salmon fishermen, they climbed down the metal ladder and fished from that platform above the river.
The walkway only goes along that rock face but there is a deep pool all along underneath that walkway and apparently it was a good spot to catch the Salmon.
I don't know if they sat down on it or stood up while they were fishing but the platform isn't that wide.
I know that you went to Blaenau for a walk so if you didn't go along this walk, then the train and A470 are both about 50 yards away!