So you've had it pretty easy for a while now. And so here is a tough one for you!
No hint. Just some guidance.
It is not magnetic
It is no longer in the entrance to the tunnel. It is along the footpath a few metres.
It is not above you, that is just the M2
Do not stop on the M2 to get this, as you will not be able to.
The complete series including the splitter cache is approx 6 miles or 9.5km and should take a couple of hours, depending on your speed. The route is a mix of fields, footpaths and lanes, which does have some styles and hills to negotiate. Have fun out there!
To split the series into two parts would result in one 4 mile or 6.5km route and one 2.5 mile or 4km route.
Here is a link to all of the caches and types in the series...