The cache is not very difficult, however might be hard to reach. You don't need to go near the rail and I don't recommend it by any means. You can and should hunt the cache from the top of the bridge. Expect moderate muggle activity, so a night hunt is advisable. The container is larger micro with just logsheet and some pens.
To open the container, rotate the lid such that the arrow points towards the magnets.
Congratulation for FTF goes to: SeanLyttle, RM00054 and Bike pirate.
Congratulation to Spooney15 for a find after nearly 5(!) years of trying!