In a Hunter T7 or T8 there is no interlock between the canopy jettison system and the ejection seat firing mechanism. The canopy should jettison when one of the handles is pulled but if it does not the seat smashes through the top perspex panel.
If the hydraulics fail you get at least 1 1/2 full deflection cycles from each of the elevator and aileron accumulators before the controls revert to manual; this is checked after shutdown on an airtest.