I recall one occasion – Leuchars Lightnings, when Q1 and Q2 were airborne, Q3-4 were being prepped coming out of the hangar, when at 0400 the TACEVAL team arrived.
The day progressed with two squadrons sitting real Q; there were more ‘Soviet’ aircraft north of the Faroe's Gap than were in all of the RAF at that time (easier to pass that today).
The TACEVAL team had a quiet day.
QRA and TACEVAL were never good bedfellows...... At Lossie in the middle of a MAXIVAL during the early eighties, the Shackleton Ops Desk received the call from Stn Ops (other side of the airfield) to pick up a no-duff classified QRA warning signal. The Duty Crew runner duly clmbed into the Sqn Q-bus and swiftly made his way to ops with blue light flashing. Leaving ops, he was jumped by a group of "intruders" from the local territorials (it was dark). Despite the shouts of "STO STOP STOP", the Q-bus was "stolen" and the duty runner bundled into the back of a Land-Rover: he was then driven off camp and dropped off in the middle of Elgin, wearing his NBC suit complete with 9mm pistol and carrying a secret signal. Fortunately he had the presence of mind to hide the pistol under his clothing and find a phone box to call in. Fortunately the QRA scramble did not materialise, but it I understand that it was an interesting intruder debrief the day after.