There was also a suggestion that a RN Wessex crash (into a sea wall I think) could have been caused by a servo jam or runaway and led to the Wessex fleet adopting the 'If in doubt, Primaries out' terminology for dealing with a control malfunction.
This was based on the fact that the primary hyd system powered the main rotor actuators and the secondary system did ASE inputs and TR. The primary system was more powerful and so a runaway or jam in that system was much worse.
A similar idea was adopted by the Sea KIng force where coupled or uncoupled indications of a control malfunction was used to diagnose and select the appropriate system off.
How could you fly with no MR servos, or am I misreading it?