New member here, but have explored many of Portland's offerings over the years.
Myself and some friends were fortunate enough to get in here possibly just weeks after OP's post, at the end of 2016. A week prior to our visit, a friend had tried to enter - without success - due to it having been sealed off at the top and bottom after a local YouTube made it's location public.
Our visit began as the sun set, and before long I recall we were navigating up muddy slopes using torchlight and some rope to pull us up.
When we arrived at the entrance, it appeared as though the metal grate that restricted entry at the bottom of the tunnel had been ripped from it's fixings.
Inside it made for a very nice explore, and ascending 100ft+ through the layers of Portland stone was pretty cool.
I would love to return some day, and did half heartedly try and locate the bottom entrance this Summer, but it was indistinguishable from the bushes and trees around it.
I have attached a photo of myself in the tunnel, and a photo of the top manhole cover, which we were gutted we couldn't use as our point of exit, having parked meters away from it. (the tunnel ended in what is now a car park)
Sealed manhole
Manhole cover from Below.
Myself and the large waste water pipe, which I believe is now disused - I could be wrong.
