Hi matty,
so I'm guessing you suspect a runaway on the #2, but want to understand how the turbine overspeed system works on the Gem? In the civillian commercial a/c maint manuals we do have a basic breakdown of system operation/behaviour, but I'm not sure about millitary manuals.
Do you have a local RR rep that can get a system description/behaviour? On civillian commercial a/c overspeed systems, the engine is normally controlled just below the overspeed threshold, but if the throttle is retarded then the enigne should 'normally' retard.
Unless you have had something else occur that perhaps held the trottle full open - was this the case, or was the engine controllable when power was reduced?
Hope this is of some help.
Brgd's
N1 Vibes
PS - there is a Millitary Aircrew section on Pprune, that I believe some groundcrew may frequent also - could try there