So just to take it further then BOAC....
What would have been the "experienced" crew response to inadvertant entry into fog/cloud during such a VFR/in sight of land or sea/clear of cloud transit, particularly when such a professional crew would have been sharply aware of their relative position to the approaching hard stuff?
Whatever their expected trained response, it is also true that CFIT happens too - and sometimes inexplicably despite such an expert crew. A survey of RN Sea King accidents in proximity to Culdrose is part testament to that - and they had radar!
So nothing really gets resolved except returning to the key issue of what specific evidence was available to accurately determine the actual conditions, aircraft state and crew actions.....not enough remains the only conclusion.