Flying Friend
with some nervousness this is my first post on this great forum. I am not a pilot - I'm an architect. The hole in the pub roof is clearly punched through - if it was a 'secondary collapse' a wider area of the roof would be involved. My guess is the space between the roof joists would have been filled with rubble from the demolition of the upper floors of the building. I think the helicopter unfortunately went straight in at some speed, the secondary event described was several hundredweight of rubble sliding down creating noise and thick dust.