Lastly, what sort of approach do you think was being flown and on what evidence do you base that opinion? In view of what I understand to be your fine ?military? flying record, how would you have flown it?
1 Brief for the approach - intentions and responsibilities confirmed
2 Identify a DH based on QFE
3 Fly the approach down to DH - QFE
4 At DH -look up - acceptable visual references? - Yes - Land.
No - Abort & Divert.
Had they done that - all would be well.
The evidence points to them descending (in a controlled way) below DH-QFE
Irrespective of the "misinterpreted" RA values caused by the valley they should NOT have descended below DH -QFE.
So why did they?
Probably became fixated on the "constant" 100m RA values and neglected QFE values OR the PF thought he saw a visual reference, deliberately descended below DH but then lost the reference, by which time the go around was made too late to avoid impact on the upslope.
Short of some additional CVR material "coming to light" for those last 10 seconds - we have to accept that the reason for the descent below DH will never be known and thats it.