It wasn't just inaugral flights, but every flight. House flag on one side and the country that was being visited on the other. I seem to remember the house flag on the Left??
Later the procedure was dropped and the only flag I saw was the Royal Standard raised through the perisopic sextant housing.
On one memorable occaision, in the South Pacific with a 707 the aircraft had just rolled to halt and the engines shut down when a young F/O playiong navigator suddenly woke up with the famous words " S*** skipper i forgot the F****** flag". Upon which a voice from the other side of the cockpit dooor said "normally refered to as the Royal Standard"!!! The Duke!!
The said F/O went on to a very sucessful career and I believe is now an elder magistrate.
Speedbird 48.