In preparation, place a highball glass or glass of your choice as well as the gin in the freezer. Place a fresh glass bottle of tonic water in an ice bath. Once the ingredients have chilled, pour the gin into the glass. Angle the glass and ease the tonic water down the side of the glass as delicately as possible. Squeeze the lime wedge into the glass. Gently lower a large ice cube into the drink, being careful to agitate the mixture as little as possible.