I've been past this place quite a few times; It's on one of my regular walks. There's a surface feature you may have missed, the BPI (Bomb Power Indicator) baffle (it was still there last time I checked). You'll also find the hatch cover kicking around somewhere nearby.
Shame about it being filled in with rubble, no chance to see what's down there. (Cans of Glitto, no doubt.)