Boyd and I surveyed the first part of the cave in 1971 - down as far as the gallery where it ended in a dig at that time. We also did the water tracing which proved it came out underwater in the river at Ilam, on the outside of the bend opposite Paradise Walk. I never saw the stream flowing down to enter the swallet - even in pretty wet weather it always seemed to sink under the base of the bramble bush where the footpath crosses the field boundary - but I have been told that it can, under extreme conditions - flow down right down to the sink.
Don't forget that the correct route to the cave from the car park is back out into the road, walk a short distance along towards Blore then use the marked footpath to cross the field where the cave is, past the big shake-hole, then turn left along the field boundary to reach the cave in the hollow. There is a stile over the fence by the cave - don't forget to replace the grid over the cave when you leave. All the details are on the DCA website athttps://peakdistrictcaving.info/home/the-caves/hamps-manifold/waterways-swallet
Matt's right - it is a smashing little cave.