It happened when the Lightning squadrons in Germany transitioned to the Phantom; also the Jaguar squadrons began life as, for example 6(Designate), losing the ‘designate’ suffix upon the Phantom FBSA airframes moving to the AD role. I forget off the top of my head if those squadrons renumbered or whether we had 111(Designate), 23 (Designate) while the Lightning squadrons with those numberplates disbanded.
The practice was mooted for Typhoon, but as I recall there wasn’t enough money nor enough people to allow the F3 and Jaguar squadron (i.e. 6) to continue with their previous airframe while the ‘designate’ Squadron worked up on type and then took over the role.
When this was done, the squadron with the old type would traditionally cease to exist on type at 2359hrs on the due day, take a minute (metaphorically) re-equip and then, at 0001, would be in a position to resume work with its new aircraft.