To those interested. Here is the report on the damage and some photos.
To repair engine and do some other stuff as well while it is out, like radiator and inter-cooler flush plus turbo service/kit come close to R40000! I am fixing it properly and not taking short cuts. I am going ahead with the repair and at this stage does not suspect foul play on the side of Alan Black when they did the diesel pump and injectors less than 3000kms before the piston failure.
I believe that the piston just was not manufactured to handle the stresses it is subjected to forever and as such will fail eventually. Only diamonds last forever they say( some Toyota owners will try and convince you that Toys also last forever but I disagree

) It is a blow to the system and the piggy bank but at close on 300000kms I can probably not complain too much.
There are NO warning signs and also NO tests that can be done to detect this early before it goes South, as far as I can gather which is a bit of a bummer. Maybe someone can research this in more detail? Furthermore I believe that I have done ALL one can realistically do to prevent premature failures with EGT probes, cooling down engine after prolonged hard use, no redline revving etc, very short oil changes and religious servicing while I had it over the last 220000kms. I also had injectors checked and replaced at 100000km intervals.
Usage history: I have never used 2SO consistently(only once used) and have also not blocked off EGR since I bought vehicle on 80000kms. I tow big loads regularly off road. I do not know how the inlet port look at this stage and if it has any relevance.
Please note that this report ONLY relate to my vehicle and NO deductions or other assumptions can be made from it!! The report is also not to be used to point or un-point fingers but are merely shared as knowledge enrichment!!!
Comments and donations welcome
CATS