"I do remember a Shack taking off at the end of the display in 1964/5 and arriving back the following day at the start of the display having supposedly been on patrol in the mean time! "
That was the one which did the singleton display over Rockall. Particularly spectacular in '64, when the Northern Lights were at their best.
HB. Wasn't the Aerodyne supposed to film the Rockall display that year? Rumour was that the sun-spot activity which produced the superb Northern lights upset so many of the Aerodyne's systems that they could not find Rockall.