Think I found the problem........
When we had a look at the engine, opening it up to expose the crankshaft, found that the bolts were extremely tight, had to use the an air ratchet to get them off. All except the two at the end of the engine where the shaft broke.
The shims, at that point were excessively worn, whereas the others were "like new".
So it seems that at some point the bolts had either:-
1. worked loose, or,
2. were never properly tightened at the factory.
Therein lies the root of the sheared crankshaft, so the next time you're under your diesel, check your bolts.
