The BAC 1-11 ended up with 4 AOA indicators, 2 on each side that operated a stick shaker and stick push to keep it out of a deep stall.
Back in those days, aircraft lacked modern flight envelope protection and on a rear engined "T" tail aircraft such as the BAC 1-11, Trident, B727 etc, if you managed to mishandle it into a deep stall you would more than likely crash. The wing shielded the engines and tailplane from the airflow so the engines stopped and the rudder and elevators became ineffective. The ailerons wouldn't be able to do much at low speed on a stalled wing and you simply sat there in a high nose up attitude, low forward speed and high rate of descent until the aircraft impacted with the ground.
Aircraft with underwing engines weren't nearly as likely to deep stall and the tailplane was less shielded by the wing at high pitch attitudes so control was easier to regain. Obviously any stall was something to be avoided no matter what type the aircraft was.
The regulations of the day took account of the consequences and likely hood of the event occurring and provided for extra protection.