The mystery of the non-starting diesel has been solved.  Unfortunately Nobby put a rag in the air intake after the engine ran in the shop.   When John and I bolted on the inlet manifold in the boat we did not see it.   Of course the engine would not start.   The rag got sucked into the cylinders, Nobby has taken off the head to clean things up.   Pic attached.   The weather is getting warmer.