All electrical power for the ejection sequence comes from battery not aircraft power supply so in the event of a loss of electrical power the hatch and canopy bolts will still activate. There are of course three routes out of a Canberra, exit/entrance door, rear hatch and ejection seat. The double skin canopy on the Canberra would require an axe to break it, a knife would be useless, a crash axe is stowed inside next to the entrance door. The pilots canopy explosive bolts were deactivated many years ago as it was found on ejection the lower leading edge of the canopy could "fold under" decapitating the pilot so the seat now fires through the canopy.