I am new to these forums and also intrigued by this accident. In the other thread
G-ARPI - The Trident Tragedy: 40 years ago today
I have submitted a post which summarizes a notion that Captain Key's airspeed indicator was erroneously reading on the high side. This idea did not originate with me, but had been extensively considered in a book, as indicated in my other post. It is indeed an enduring mystery as to why Ticehurst - who in his P3 position should have been monitoring cockpit activities - did not notice the droop retraction and associate it with the stall warnings.