When supporting Northern Q with the FunBus, it was normal to give the F-4 crew a position update after AAR. In those days we only had Carousel IV and Omega and the INS wasn't automatically updated by any external navigation system such as DME or GPS. So it was monitored carefully by the on-board food-powered universal navigation device.
INS gave position to a tenth of a degree; however, it has been known for the position to be passed to the F-4 with a spoof extra place of decimals....
Why on earth a decision wasn't made to move the FGR2 to Leuchars, I really don't know. The Lightning wouldn't have operated as far from land or a tanker as the FG1; I doubt whether operating miles from anywhere without comms or navaids would be acceptable these days.....
