PB111 tunnel??

I've adjusted to position of the PB to your co-ordinates, thanks.

Don't know about the tunnel. The entry I saw was a short concrete-sided trench leading to a collapsed tunnel. I suspect this one might be Japanese. At least two other PB tunnels, 121 and 312, have holes cut into the side of the tunnels some distance from their entry, which would afford a second exit point in a different direction. The one entry was a shortcoming of the original plan.