Thought I better go see if this is doable , got the mighty six out and headed to the A4 where it crosses the river thames , first two pictures taken either side of the river and are stone , then headed to Marlow , bucks and another old thames crossing , found another two , one looks like steel the other cast iron , to make this challenge a bit easier , iron, steel or stone wins.....
One, is never going to be enough.....