Lightning canopy restrictor mechanism
A February 1962 copy of Lightning F1 Pilot's Notes states:
"Normal operation of the seat
When either firing handle is operated the canopy is jettisoned immediately and removes a restrictor from the time-delay firing unit. After a delay of one second the seat is ejected and the drogue gun, which is operated by a static rod, fires half a second later ......
NOTE: The seat cannot eject if the hood fails to jettison."