Hello 105, your info about the rope attached to the pennant suggests three other possibilities, none of which I’m comfortable suggesting, simply because of the rarity of chance they involve.
A:The ensign was flown from a landingcraft, most likely a Landing Craft Infantry, since a Landing Craft Mechanised (tanks or trucks carried) or a Landing Ship Tank would most likely have flown a larger ensign.
B: The ensign was flown from a motor torpedo boat or air-sea rescue launch (same hull as mtb but less well-armed).
C: The ensign was flown from an X-craft (miniature submarine with a crew of 4) some of which waited submerged just offshore (i.e. in less than 20 feet of water) to surface and act as “marker beacons” to the landingcraft approaching the beaches.
I have placed the above alternatives in what I regard as the order of likelihood, from most to least likely.
Dimensionally, I do feel it may have been too small for either A: or B: but that’s not to say it could not have flown from one of those vessels, as I’m certain it would be a case of “grab what is usable”, supplies of such items being at that time not the most organised.
Again, thinking on this far of an extended limb is not the most relaxing of academic pursuits, but it may provide you with further avenues of research.
Kind Regards 105, Uyraell.