In one of the Tornados there is an emergency. An automated alarm is sounding. The navigator instructs the pilot to dump superfluous fuel and gain height to ‘buy’ extra time.
I'm assuming that this emergency has occurred at low level. The immediate actions would be to pull up and zoom climb while conducting the rest of the bold face drill. Dumping fuel would not happen at this stage, in any event, it happens quite slowly in the grand scheme of things and would not lighten the load noticeably.
A more reasonable sequence of events would be a catastrophic loss of thrust resulting in an emergency jettison and our man on the ground getting hit by the falling drop tank. This is still in the realms of improbable fiction but at least it *could* happen.
A torrent of high octane aviation gasoline cascades towards terra firma - down onto where MacDonald stands smoking. With a whoosh, he is evaporated.
Jet aircraft don't run on "high octane aviation gasoline", piston aircraft do. Jets use AvTur which is pretty close to kerosene and is damn dear impossible to set on fire. If you threw a lit cigarette into a tank of the stuff it would put the cigarette out.
Emergency under control, Flight Lieutenant Siân MacDonald requests her navigator plot a course for RAF Lossiemouth, and home.
Despite the name, navigators on Tornados don't generally navigate. The pilot does. The Weapon System Operator (WSO) - the new name for people in the back - would be responsible for updating the nav kit to make sure the aircraft thinks its in the right place, for cueing weapons to target and being an extra brain and pair of eyes in the cockpit.
With a critical emergency you describe above a PAN call would have been issued and D&D would have given the crew a steer to the nearest suitable airfield.