As the mist clears with this accident investigation (and credit to the AAIB team for keeping the industry comprehensively informed at the earliest), whatever mechanical / design flaw developed that night, it appears the pilot may have found himself in unfamiliar territory:
Approximately 180 degrees out of wind, 400 feet AGL, one engine out, at night (possibly goggles) AND THEN the remaining engine fails!
I keep thinking about his background (Chinooks) and his present job (EC135): both NEVER practice total engine failure(s) to the ground.
(Possibly) decades of practical inexperience with EOL's - further aggravated by the spatial predicament he found himself in that evening. RiP.