I don't think we should read too much into the weather at Gillingham Hall at the time of the accident from what Aga has said - as I'm sure he would agree. Yes on the face of it it was simply foggy and VFR flight could not have been possible - but I'm not so sure. We all know mist and fog forming on the ground, as he says it was a mile or so away, at 18.40 could have barely affected vertical visibility. Indeed I think it is interesting the full moon was still discernable at 21.00 - a long time after the accident time. It has to be quite possible that the vertical vis at GH at the 19.30 take off time was pretty clear - clear enough for a vertical climb to be made using the full moon as a visual reference if required. One presumes the crew might have known there was fog building in the area but then maybe expected to transition to forward flight once above any fog in the area - say at a height of 100ft or so.
The location of the accident is interesting - thanks Silsoe. I suggest it is too far away from the take off location (assuming take off within the grounds and say 50m from the hall) for there to have been loss of control during the vertical climb through fog, as some are suggesting must have occurred. More likely is that either something was hit then (where was the damaged tree?) and perhaps a rotor blade damaged that then failed say 10 secs and 400m later, or perhaps more likely still, having made a successful vertical climb to the 100ft of so required to clear the surrounding trees, transition to forward flight was made too early, before being well above any surrounding fog, and maybe the crew, expecting to be effectively VFR on top, became disorientated and lost control in IMC. If this hypothesis was true, perhaps if the whole departure profile had been on instruments this could have been avoided by ensuring sufficient height was reached and a positive ROC was instigated on transitioning with forward pitch at the top of the vertical climb. Of course, all just theories.
I must say I am surprised not to see evidence of a permanent helipad at the hall on Google Earth, though maybe it was built after the 2006 image. I would definitely want to have a hard surface to land a wheeled 139 on regularly.
With regard to the crew it would be interesting to know if the co-pilot was IR - I suspect not. Again, be interesting to know what sort of total and IR time the captain had.
It is totally unnecessary and indeed it would be very negatively burdensome to the industry to change regulations as some have suggested by licensing private sites for night use etc. Many of us frequently operate helicopters into private sites at night perfectly safely with whatever level of lighting is prudent. Helicopter pilots - particularly those involved in corporate ops - need to have the intelligence and judgement to make safe decisions, all the time. At private sites even if they were licensed there would be no weather for example, so sensible judgements must be made about night take offs particularly and many are best considered as IMC departures anyway.
Where there could be a case for new regulation is in the employment of pilots. Given some of the comments on this thread about boss pressure, maybe any employer of a pilot (outside of an AOC operation) should have a licence from the CAA, granted after an interview and briefing session with the CAA (which they can pay for of course) to establish their suitability as an employer, and during which time the key employing passengers were taught some basics about helicopter regulations and safety - eg no IFR flying in singles. There is a lot of ignorance about, unsurprisingly. This licence would be anually re-issued and any comments from current or ex-pilots sought and considered by the CAA.
Helicopter pilots need to operate much more on their own initiative than fixed wing pilots and must ensure their flying is safe by being highly competent and responsible for their own judgements and decisions, but a process to minimise employer pressure (through education as much as anything else) might just be the most valuable outcome to corporate ops safety from this accident, if it is found to have no mechanical cause.