I can't see anything, probably because I'm on the work's computer and Youtube is blocked. However, if the dive looks like it goes to/from daylight and there's a short drop leading to the sump at one end and a chamber at the daylight end it would be Gravel Hill Mine. There's two levels, the upper eventually becoming low and silted. and the lower bending round and leading to the free dive (approx 25ft) out to daylight again.