Not GMC but I remember an instance in the UK back in about 1970 with a Cessna 150.
Filed IFR from Stansted routing outbound via Dover for a departure about 3am local time.
The controller at the centre (London ATCC) responsible for departure clearances issued the clearance, route as filed, to maintain not less than 150 kts!(he'd filed a cruise speed of 85 kts).
That particular controller (who wasn't popular with his colleagues) was also about to go off duty.