Brian,
I have no wish to denigrate Mr Holbrook as he has been asked to describe a relatively fleeting moment many years ago. How fleeting may be judged by the evidence he gave to both the BOI and the HOL Committee where he indicated that that his sighting of the aircraft was limited to to a 5 second view; he also assessed the speed of the aircraft as "somewhat faster than Sea Kings in level flight". According to MOD that would be an airspeed in of in excess of "100-110 knots".
In his evidence to the FAI however, he indicated that he watched the helicopter for some 25-30 seconds whilst manoeuvering his yacht around fishing boats and that the aircrafts speed was "60 -80 kts." We know, however, that the average groundspeed of the aircraft from the ATC fix to impact was 158 kts. A significant difference.
In my view the failure to obtain evidence from the only other witness is unforgivable.