As mentioned earlier TO, that question certainly taxed the minds of the human reliability experts. As with other purely British controlled systems, NATO always had issues of ultimate control. Would we go it alone and effectively force the nuclear issue?
Of course the Jaguar was not the only singlle-seat strike aircraft on QRA in NATO.
The main precaution was control inside the gate.
now I am speculating but once that gate was opened, if the aircraft received a scramble order, unlike Strike Command, distance from take-off to target was so short that launch was unlikely to be ordered with out release too.
In the event that there was a hold post gate opening then I believe other physical restraints were available to the fore commander.
Once airborne then it would have been strictly one man one bomb. There was no magic permissive action link as with US weapons and Dr Strangeglove. We could not afford the technology nor did we think that available technology would hae been sufficiently robust.