For BHD from Guernsey on an IR training trip last week, in a PA34, callsign 'Fasttrack xx'. At FL100 just handed on to London Control:
US: London Control, Fasttrack XX, FL100 direct Berry Head
Him: (Long Pause) er, Foxtroxt Sierra Tango xx was that?
US: Affirm London, it's Fasttrack xx, FL100
Him: Confirm Your callsign?
US: FASTTRACK xx
Him: (deadpan voice) Ah, roger fasttrack xx, it was the 160kt groundspeed that fooled me...
Much appreciated by all on board hee hee