Diplomatic Clearance could cause confusion on-air. I can recall an instance when a squadron aircraft was allocated for a special mission requiring Dip Clear and its callsign was used in the paper work. Unfortunately it went u/s before the event and was replaced by one from a different squadron, which retained the 'official' call. Two days later, our aircraft now being serviceable, I was using it for a 'Jolly' to Nicosia when I heard this 'namesake' calling so there were now two of me/us. Can't remember how it all ended, think I closed down on H.F. W/T and reverted to VHF only for the short trip.