It is a curious fact, and one to which no one knows quite how much importance to attach, that something like 85% of all known worlds in the Galaxy, be they primitive or highly advanced, have invented a drink called jynnan tonyx, or gee-N'N-T'N-ix, or jinond-o-nicks, or any one of a thousand or more variations on the same phonetic theme. The drinks themselves are not the same, and vary between the Sivolvian ‘chinanto/mnigs’ which is ordinary water served at slightly above room temperature, and the Gagrakackan 'tzjin-anthony-ks’ which kills cows at a hundred paces; and in fact the one common factor between all of them, beyond the fact that their names sound the same, is that they were all invented and named before the worlds concerned made contact with any other worlds. –Douglas Adams, Restaurant at the End of the Universe
In this world, gin and tonics are a summer favorite made popular in the Commonwealth during colonial times for its antimalarial properties. The cocktail was originally concocted by the British army in the early 19th century as an additive to the bitter quinine potion used to treat and prevent the mosquito-borne disease. Gin was chosen as a mixer since it was already distributed as a ration to soldiers in India. Initially the drink consisted of a mixture of water, sugar, lime, gin, and quinine. With today's tonic waters you would need to use a significant amount more in order to reach the original antimalarial treatment proportion.
1-2 oz gin of your choice
Tonic water (Schweppes is always a safe bet)
1 Lime (or lemon, orange, or cucumber)
Pour the gin over 3-4 ice cubes in a glass (chilled, if you wish). Add 2 parts tonic to the gin and 1 part soda water. Which fruit to garnish the cocktail is a topic of debate, but I typically top off the drink with a squeeze of lime juice and garnish with a slice of lime. According to gin "connoisseurs", you should use lime with Bombay Sapphire, Gordon's, or Tanqueray original; lemon or orange with Beefeater; and cucumber with Hendricks.
A note for those of you ordering this classic at a bar Stateside, make sure to clarify that you want a bottle of tonic and not just soda out of a gun. Having your gin topped off with flat soda water is one quick way to ruin a good G&T.