Here goes but don't quote me -
Non acclimatised cabin crew are allowed a maximum FDP of 13 hours.
However in flight rest of 5 hours is provided in a bunk, therefore maximum FDP may be increased by half the in flight rest provided ie 2.5 hours. Therefore max allowable FDP is now 15.5 hours.
IAD JNB direct is 15 hours block.
Hence with a 1 hour delay, the cabin crew were out of FDP by 30 minutes.
THE CAPTAIN, HOWEVER HAS THE SOLE DISCRETION TO EXTEND A DUTY PERIOD BY A MAXIMUM OF 3 HOURS, PROVIDED HE BELIEVES THE FLIGHT CAN BE COMPLETED SAFELY!
These individuals have a lack of respect for the chain of command ,their profession and their passengers.