Looks mental that siologen! We were there less than an hour after low water, so I'd say tideway now plays a part. Might have to have a rethink or pay more careful attention to tides, yeah. It would appear the inverted siphon crosses over something it would've otherwise clashed with, no? Wouldn't the small hole be there to drain away what would otherwise remain there after storm flows? A bit like TheVicar described in his Labywrinth report. Or is the whole inverted siphon a flow control measure to slow everything down perhaps? 50m long! Whatever it is I've gotta see it and am very grateful for your input.