Contary to popular belief about Nelsons Navy, Rum, or strong spirits was the issue of last resort.

Beer, a gallon a day while it lasted or Wine, particullaly when in Mediteranean Waters, (Cape Trafalgar ain't that far from Gibralta).

I doubt wether Port would have acted as a presevative, and I am inclined to believe the Brandy theory, if for no other reason than double refined spirits, ( a rather crude form of alchol) were used as a form of primative disinfectent by the more enlightend Surgeons, and as a preservative by naturalists. If I recall correctly, Nelsons body was first taken to Gibralta where the normal preserving spirits would have been available.

With regard to the French connection - "Watch the Wall, My Darling, While the Gentlement ride by"

Gareth