What were Royal Navy ships required to provide by law when entering the Port of London?
Correct answer: Barrel of rum

Castra
Even today, a ceremonial barrel of alcohol ( wine, rum or brandy) is presented to the Constable of the Tower of London by the captain of every Royal Navy vessel that moors at the Tower of London wharf.
It's called "The Constable's Dues"
It's a very formal ceremony.

baymax
see even back then they had the sense to limit the age of a young drinker, good for them!!

Player #3532789
It is also apparently where we get the word groggy from. The hangover from the grogg!

RubyUndertaker41803
In 1756 citrus fruit was understood, but Scott of the Antarctic and his men suffered because of poor diet, lack of vitamin C!!