There are a couple of reports from witnesses inside the pub that do not ring true with the crash evidence. They report seeing the ceiling buckling from within and then shortly thereafter something that caused an 'explosion-like' effect within the pub reducing visibility in dust and rubble. This would suggest a semi-controlled landing on the roof followed by the relatively great weight of the aircraft collapsing the roof onto the revellers below... all in relatively slow time.
However, all 3 crew were killed, which does not fit with that description. When helos suffer close-to-ground mishaps they impact at a relatively low ROD and the crash is survivable UNLESS....
1. Damaged rotor blades enter the cabin
2. Wreckage enters the cabin
3. A post crash fire overtakes the opportunity to egress
We are told that all wreckage was confined to the immediate crash site. The damage evident to the airframe appears consistent with about 30deg nose down at high ROD, so high so as to make the impact non-survivable for the crew. I believe that 2 crew face forward and the other is in-rear.... It would be highly unlikely that ALL 3 would perish in a low ROD crash.
There was seemingly no post-crash fire which always raises the suspicion of fuel exhaustion, however we are told that they were RTB at the end of a long(ish) task so we would expect the fuel level to be low. To conduct a night, constant-attitude EOL, into what looks like a dark, vacant lot at night is plausible. Personally I might have chosen the large, flat, well-lit traffic intersection that it faces only 20/30 metres away. Certainly the aircraft did not run-on at 35~40 knots after touchdown... In fact it seems to have had no forward speed at all as the impact footprint in the pub roof matches the footprint of the helicopter.
If an aircraft in forward flight suddenly plummets for some mechanical reason then it retains most of it's horizontal velocity until it reaches the ground. We see no evidence of that at the crash site. There is no peripheral damage to the relatively fragile pub roof that might witness horizontal velocity.
Perhaps the aircraft was close to the hover at operating height? Vortex-ring is a possibility but this pilot's stock-in-trade was low-IAS urban surveillance from 1000-1500' at night. In any case the height would permit some attempt at VR recovery which of course requires forward IAS...which is not witnessed.... so it would seem very unlikely.
From the above one might deduce that the helo suffered a catastrophic mechanical failure at low/no IAS at height such that the pilot had no further control over the aircraft. The crash site was not one of his choosing and the crash was not survivable. It would have been over in an instant and those who perished both crew and pub-goers would not have known much about it at all. That, at least, should be of some comfort to those they leave behind.