I read "Raising the Dead" a little while ago, and have a question for those that have read this and are trained in the black arts of tech diving.

How come he couldn't wrap the primary light cable around his neck when it was off his hand? The book said it was because he was wearing a helmet mounted camera. I don't know why the helmet camera prevents normal wrapping around the neck, but I have never dived with a can light.

Im not sure. But remember he was diving on a rebreather (MK15 I believe) and so he already had the breathing loop around his neck.

I don't think the breathing loop was an issue, just the helmet/camera.

Would it be that to release the cable looped around your neck you would dip your head rather than unwrapping it completely?
If so then the camera on the top of the helmet would make that difficult.