in an improvised CATIII approach.
That sums the whole thing up. PIC means PIC. Rules are rules. Going below minima THAT far, trying a NDB approach with 200m is... just plain stupid. And that decision rested with the PIC, no matter who was in the cockpit or the rear.
I would understand (not saying one should do it) an approach attempt in maybe 100m-200m less visibility than required, as transmissiometers and observers might be a tad off the mark and fog often isnīt solid... but under these conditions? You go to your minima IF you feel you need to prove a point and then you pull up and divert. If you`re really smart you donīt try it at all and proceed to the altn, using the remaining flight time to organize ground transport.