TZ - ignoring a couple of obvious banter-based responses.... 617 (and 120) were awarded their standards before they'd completed the 25-year qualifying period as recognition of their service in WW2. This has been taken as giving the two units a status in the RAF that trumps seniority.
When the V-Force was to be reduced in the light of the RN taking on the deterrent, one squadron was to go at Scampton. The documentation from the time is absolutely clear on why 617 survived and 83 squadron went - the early award of the standard saved 617. I assume that this may also have applied when the Tornado GR 1s went to Lossie with 27 renumbering as 12 Sqn, past precedent would have suggested that the other Tornado unit should have renumbered as 208 (so long as it was junior to that numberplate), but as it was 617, it was 208 that went.
Time to award myself the
smiley (not for the first time), I fear...