This has happened three times this month in Luanda, once not even for the president, just his brother.
The BA flight was also delayed for nearly an hour 6 weeks ago as the president's office called to say 2 VIPs would be arriving late.
BA had already op-upped 2 people from WT to WT+ then WT+ to CW, CW to A etc
Had to come along and tell them that they were being bumped back down.
What a hassle, but as the pilot put it "when the president calls, we listen"