I'm sure that everyone on this thread has tried to fathom out what happened and I have to admit to my fair share of speculating. OK, so I'll get shot down again for speculating but have a possible idea of what might have happened....
On PB's way south, abeam the London Eye, the following exchange was made with ATC.
At 0757 hrs, G-CRST was abeam the London Eye at 1,500 ft and the pilot said:
“ROCKET 2, I CAN ACTUALLY SEE VAUXHALL, IF I COULD MAYBE HEAD DOWN TO H3... H43 SORRY”
The ATC controller replied:
“ROCKET 2, YOU CAN HOLD ON THE RIVER FOR THE MINUTE BETWEEN VAUXHALL AND WESTMINSTER BRIDGES AND I’LL CALL YOU BACK”.
My point now is that the clearance was for a hold "between Vauxhall and Westminster Bridge", and yet PB didn't go anywhere ( relatively ) near that designated hold. In fact the hold that he started flying , (it looks VERY much like the extended hold for Battersea, which is between Battersea Bridge and Chelsea Bridge ), was between Chelsea Bridge and Vauxhall Bridge.
IF, and it's a very big IF, he had mind shifted his position ( or mis-identified a bridge ) to the hold on the UK AIP H4 extended hold , then the right turn he immediately made on receipt of onward clearance would have been into clear unobstructed airspace.
The fact that the ATC controller had earlier offered him the option of flying up the Thames as far as the London Eye for an "extended hold", might have been a hint to him that he was further South West than his original clearance.
In marginal conditions , whilst in sight of the surface, but only just , it could be relatively easy to mistake one bridge for another I imagine ?
His flight path in those last few minutes look like text book stuff , for that Extended holding pattern, but just a half mile too far East.
