We did start by going up into the void, from where you can see the way on vertically down. However, although it's a big void, it's roofed and walled with hanging death, some of which you would disturb if you started removing the floor (which you would have to to get any further). So we concluded that this method would be foolhardy and retreated. Then we spotted the actual way on at a lower level in the choke, which joined up with the route seen from above, but on the other side of the narrowest point. We could obviously get through this way, but it was very very tight.
Chris.