Hi Graham,

Well that was an unexpected find; good work!

When timing chains "jump" it most commonly occours when you shut down
the engine, however in your case it happened during a slow cruise.
With enough slack the chain will actually start to "ride"/ramp up the
teeth and eventually hop on the gear. Had this happened to my old Alfa
I would be replacing valves or much worse.

You can remove the timing cover without head removal, but the front
edge of the pan/sump should be slightly loosened/lowered. In this
method great care must be taken to not damage the Head gasket upon
reassembly and sealant should be used as the gaskets have already been
compressed and might leak.

I was taught my mechanic ethics at a young age by an old salty English
mechanic to be very fastidious; he would actually grab a torque
screwdriver and check the tension of my hose clamps!!! I hated his
methods then, but now I really appreciate his mentoring for it
contributed to my low re-work percentage.

I would say that if you engine is fairly fresh (under 160,000 km) then
pulling only the timing cover alone is ok. But if your engine is over
that mileage I would pull the head, have a valve-grind performed, and
replace the sump gasket.
The chains and sprockets are very reasonable so perhaps you might
consider replacing these along with a new tensioner assembly.
(Depending again on milage)

Highest regards,
Blake