I have the above which I have tried to reduce with a softening additive in the oil. It has helped, but obviously I'm just putting off the dreaded day......
Presumably it is a full engine and gearbox out job to fix . Question is... what other inaccessible jobs should be tackled at the same time to avoid ever having to do this again in my lifetime? Mine is the M25/629 engine with 5-speed gearbox, and has done 100k kms in its 35 years, and seems to have been well looked after by a French Garage proprietor for 25 of those.
Finally, should I worry about crankshaft bearings being a root cause of this failure or just accept it as an old age one on this seal?

Many thanks,