After scratching my head etc etc, I think the mystery is solved. It's not classified - Flight magazine have truncated the scan - the scans must come from bound copies and parts of the edges of the magazine must be hidden in the binding. See the attached picture and you'll notice where the gaps are (rough approximation). Yes, there is a bit missing in the centre of the Flight drawings. Looking very closely, the portholes visible on the drawing of the front half, just behind no.2 engine, are those in the bombdoors which are shown closed. It still looks as though they haven't shown the bombracks which would be inside, when the doors are closed.
