Good detective work Steve, well done.
It is Dyserth and the bridge is across the Afon Ffyddion. In fact it is near the top of the very impressive Dyserth Waterfall. Tellytubby and Rhuddlan have many times both walked over the concrete bridge together but I'm sure that it was the weight of the floodwater this year that finally finished off that old bridge. Anyway the new bridge is a splendid replacement so well done to all the people that were involved in the construction of the new bridge.
I lived in Dyserth for over six years and when I took my wife to see the bridge, I parked the car in Dyserth High Street and went through Bryn Y Felin to get to the footpath. We had never been there before and it was a lovely experience to see the old detached and terraced cottages it was like a reminder of times gone by.