The reverse procedure involved the Flight Engineer pulling back a reverse arming lever until it dropped into a detent position. This allowed the propellor pitch to pass through three pitch locks and produce reverse thrust. The standard landing briefing by the pilots used to be something like: After touchdown I will call for Superfine, Brakedwell and then Reverse as ordered.
The Khormaksar overrun was caused by the RAL not being in it's full detent position, thus producing forward thrust instead of reverse when the power was increased to slow them down, until it was too late to stop at the end of the runway. I seem to remember the captain had just been promoted to the LHS and the F/E was new on type
Were you on 78 Sqn? I left 105 Sqn in August 1966 for the Brit fleet. During my time in Aden I was lumbered with a Board of Enquiry for the 78 Sqn Wessex which, due to a loss of power, dropped the underslung Beaver it had just rescued from a Radfan wadi where the army pilot had force landed with engine problems. I was very very relieved when they opened up the suspect Wessex engine (sealed by the plod) and found severe sand induced damage along the full length of the compressor.