Done a few of these myself, and arranged a couple whilst on ground duties on ops. Although not a comp, the best was a hospital flight from Gib. Very sick young girl going to specialist in UK. Wheels up, and passed to Spanish ATC, cleared direct LHR. Approaching London, everything was cleared out of our way. One speedbird, when passed holding instructions, questioned the priority of an ASCOT callsign (presume he didn't hear the prefix), and was immediately offered diversion to Manchester! All went quiet. Helo on the taxiway, little girl away (she survived ok), then nearly 2 hours to get out under our normal callsign!
Love to knock movers, but have seen them pull out all the stops to help and really come through on the day.