None of the schemes I was aware of pre-date Celis in 1985 but it's apparent upon actually reading Celis [which I hadn't done previously] that he's only improving on an existing state of the art, so I was entirely wrong about that. That state of the art was pretty dire by my reckoning, but it's clear that it would have worked so I was entirely wrong and I apologise for being so assertive when in fact I clearly didn't know what I was talking about.