disco 200 tdi white smoke

230k on disco 200tdi. starts ok runs ok for 10 seconds the starts to white smoke on tickover and doesnt clear and if left intermitently gets even worse and looks almost bluey. using water. had head gasket done 18 months ago didnt make a difference but kay seal solved it for a little while. any ideas???

head could be cracked

I would also guess a cracked head or that it is slightly warped. Skimming might sort out a warped head (which could explain it was ok for a while after changing the head gasket last time).