dalek
<<The big problem with your theory and that of the AM's is speed.
The aircraft impacted at IAS 149 (Cable)
The aircraft was at lower speed a minute or so earlier ( RACAL or Holbrook)>>
A long time ago I recommended that anyone interested in this case download Boeing's Analysis of Available Data (Mitchel) back in 2002 (as I recall) it was the first available decent go at old fashioned analysis it was nothing to do with the simulation if you disagreed with parts of it, it at least served as a framework and aide memoire for you to do your own sums and was an easy reference for some of the basic data.
In it, Mitchel had it from dist/time analysis and using the best available data for wind that the a/c most probably had held a constant airspeed for the sea crossing up to waypoint change, where it made a turn to the right and then slowed down the increased wind as it approached and crossed the shoreline masked this slowing down in airspeed the steady intermediate power level supported the scenario of letting the speed wash off as they approached the shoreline.
I posted some time ago annotated charts showing that, had they continued to waypoint A and commenced any reasonable turn (30 60 bank) as they crossed the shoreline, their approach heading of 035 mag (that was their track on that final leg from waypoint change to the area of the crash and as was found on the HP's HoSI course selector) was ideal for a graceful swing around the back of the light house with plenty of room for safety at their altitude even at high cruise speed.
They would have been below the orographic cloud (800ish ft) and above the layer of mist running up the slope they should have been able to see the lighthouse intermittently from above when they swung around it it would have been an impressive demo, perhaps.
Waypoint A just happened to be where the LZ with which they were familiar was.
Although most probably able to make out the ground, they would surely not even have gone in even as close as waypoint change on visual alone or TANS at speed as they would not have wanted to cross much to the right of that LZ (as they unfortunately did) the manoeuvre was safe only if they got the landfall right they were correctly on track to waypoint A up until waypoint change yet they turned right while evidently in control. The most logical explanation is that they had something that they were relying upon to mark that LZ and that this reference was for whatever reason out of position - ½ a mile or so up the hill explains the turn off the correct track and that they closed with the landmass sooner than expected, missing the shoreline crossing with MALM Forbes not yet at his window position.
If there was any fault at all by the captain, it was the disposition of his loadmasters if MALM Forbes had been, say, checking the CPLS CDU then it would have been a good idea to have the other loadie up at the side window, so critical was it to keep an eye out for the moment of crossing the shoreline.