I only flew the turbine Mk10 at Ternhill - the engine was at idle for the EOL, and there was no link to the collective in that version
Yes, IIRC, the "flight idle stop" switch was first moved to the "ground" position. When the throttle was closed, the engine ran right down to ground idle and you were committed to land because it was unlikely the computer could accelerate the engine again without causing compressor stall if a go-around was attempted. If you advanced the throttle quickly with the computer engaged, it would lock up (and set off a lorry type warning horn behind you), to prevent engine damage.
However, one certain course colleague of mine flew with a certain French exchange QHI who didn't like flying "fuel computer in", allegedly because of his previous background flying early Allouettes, which didn't have one. Much of his hard working studes' flying was done in manual throttle (not the normal way on the RAF course).
On the day in question, my colleague was working hard as usual, flying in manual throttle. He was then directed to carry out an EOL at Tern Hill, which was entered without putting the computer back in (again not the normal thing to do).
After landing, and a quick debrief, the stude was told to get airborne and do another EOL. The engine was still in manual at ground idle (not the normal configuration). A little confused by now, he opened the throttle which instantly surged the engine, causing a ten foot long flame to exit the exhaust. Engine change time!
That occurred just before lunch. By mid afternoon the same day we were directed to sign as acknowledgement of a new flying order, which prohibited EOLs in manual throttle.....