With the facts that are now coming out and as an ex helicopter pilot myself I find the sequence of events leading to the accident very strange. Clearly there is more than we currently know for an experienced helicopter pilot to do what he did.
On the face of it flying from Redhill to Elstree to decide to divert to Battersea in these weather conditions was a strange decision. An ILS approach into Heathrow would be the safe option after climbing to a safe altitude. Then the cost of landing at Heathrow could be a factor. But to fly down the Thames to land at Battersea in freezing fog? Odd. Maybe icing was becoming a factor and he did not want to climb? It's all a bit strange at present.