Witnesses in the pub and impact speed
Agree, geebee50: from reports at the time, I recall:
There was a bang, loud enough to stop the band playing.
Someone had time to quip (and be heard saying) that the band had brought the ceiling down.
Then a helicopter came through the roof.
That's probably not the signature of a 3-ton helicopter smashing straight in vertically at 200mph. Not unless the roof absorbed all that energy - equivalent to that of a 40-ton truck at highway speeds - held together for a couple of seconds more, and then gave way.