The cable on Dekay`s 340 is hanging out of the hub. I can see a rubber bush on the back of the hub and the end of the outer cable has a flanged ring of the same diameter as the bush`s outer. Is there a clamping device missing to butt these together or does the flange go inside the bush. If so how far and does the bush have to come out first and fit to the outer.......Ive fettled it temporary with an overtube and clamp,seems ok for now. Mr Haynes is no help with drawings or instruction.

There's no clamping device for this. The rubber bush should be tight enough to hold the cable outer casing in when its inserted up to that flange. The cable outer sheathing can break, and I'm guessing that's what's happened in this case.

Cure is a new cable.

from memory I think there was about 12mm of outer sheath forward of the flange that pushed into the bush. does it sound like some of this has broken off. ?

Sounds that way, there's a weak point just after the back of the hub, so they break there normally, appearing as though all is well, as it gets flexed on tight turns. With mine I could push it back in and it would work, until you took a tight left turn, as it would pull it free again. Indeed, a new cable cures it.
Pete