New primary chain arrived.
I laid it down by the side of my existing chain and the old chain was 3/4 of a link longer over 70 Links.
No wonder that my old chain went from dead tight to 1" of play when rotating the engine.
I fitted the new chain and there is ½" of play all round the engine cycle.
My worst fear was that I had a bent shaft, Pheew.
Thanks to all for helping to sort this out.
Roy.