It's reminiscent of another QF loss of control, when a B707 - I forget the model - went out of control in the cruise en route to Bahrain, late '60s/early '70s.
There were signs that while out of control the aircraft had experienced up to +3G to -3G, and may have been inverted at some point.
The reasons were quite complex, but I vividly remember the Captain saying, after we had got the passengers off and into a hotel, that he had only managed to regain control at 6,000 ft (I think it was) by using primary instruments, throttles, "stick and rudder", and doing exactly what he would have done in the Tiger Moth he had learned in.