And now the answer (maybe)
Answer - nothing! No train, no tunnel...
There *were* clues!
1 - Original GPR and geophysics images...hilarious! Details of tank barrels, hatches etc, etc.. Anyone that knows ground radar and the likes, can tell you that picking up such details, inside of a *tunnel*? No chance!
2 - LIDAR - no evidence of earthworks, backfilling of tunnel entrances...nothing
3 - Academic and *actual* geophysical experts investigations, conclusion: 'there's nothing there'
4 - Despite apparently knowing *exact* entry points, having plotted the full course of tunnel through their survey works etc...they dig in 3-4 different places!
Fair play for having managed to get gullible souls to fund all the moving around of dirt though! :lol:
Over-ground, underground, wombling free...