Fortissimo
While there is no evidence for inccapasitation apart from the appaulingly bad approach that was so far away from the norm for an experienced pilot who had used this airfield before, there is also a lack of reason for a pilot with all his faculties intact continuing an approach with the knowlage that the touchdown point would be that far down the runway.
Unlike some of the more far fetched stuff on these forums both these theorys cant be ruled out according to the only reliable form of information avalable (the AAIB prelimenary report ).
The chances are that the full reasons for this accident are unlikely to be understood even after the full AAIB report is published unless something positive comes out of the postmortem on the pilot.