Woahh!
We don't know that this is off the bridge so at this stage it's all conjecture; it might have been a spare from somewhere, it might have been used for tensioning a cable or similar. It might even be off a telegraph pole and some idiot was going to throw it down the shaft.
I also cannot understand why, if somebody is going to risk their life to remove about a quid's worth of scrap rusty iron, and then drag it up several levels and haul it up a 50' shaft why they'd abandon it on the surface.
As for taking the bridge down. OMG please no. It's one of only two bridges in slate mines outside of Blaenau Ffestioniog and absolutely needs preserving.
If it becomes unsafe to cross (I personally think it already is) then there needs to be another solution to ensuring it isn't crossed.
I certainly think people need to be warned that it may have become unsafe to cross; but it's not necessarily the automatic conculsion.
my orders are to sit here and watch the world go by