After working on the original for a while I decided that I still really didn't like it.
At this point I had nothing to loose so into the bath it went! A combination of water blasted from the shower, bleach and a scrubbing brush resulted, not unexpectedly, in the paper weakening.
At this point it reminded me of cave paintings, and the cracks and fissures you get. So I deliberately tore the painting up along these weakened parts and re attached them to a supporting bit of paper leaving the tears visible.