Despite numerous searches haven't as yet been able to establish why the flags were raised. This leads me to conclude that perhaps the date is not one which actually relates to a specific anniversary, rather a moment in time when the opportunity arose.
With the flying of the Commodore's Burgee I did suspect the reason may have lain with one of Queen Elizabeth's Commodore's. I did discover one very interesting piece of information which may or may not be related. Commodore Marr who passed away in 1997 is the only Cunard Captain to have a sea burial. Further, I have seen commentary which states the event took place aboard QE2 and I believe the ship's captain at the time was Ronald Warwick. Disappointingly, I cannot pinpoint when this particular event took place and therefore establishing any relationship to the flag flying.
At the risk of going a little of topic, can anyone confirm when and where the late Commodore's burial at sea took place?