Morning Mo,
The rocker shaft broke on my 300Tdi a year ago on the way home from the last Sodbury. There was no indication that it was going to go, but it made a right mess where valves hit pistons etc. The timing stuff was all intact so no clue to why it should happen.
The delightful Frida ^^^^ sorted me out, in an engine sort of way, before you jump to any conclusions.
Not a lot of help I know.