The mint should be put in the shaker first. It should be torn up by hand as it steeps better. The gin should be added then and allowed to stand a minute or two. Then add the grapefruit juice and then the lime juice. Stir vigorously with ice and do not allow to dilute too much, but serve very cold, with a sprig of mint in each glass.
Gin, Grapefruit juice, Lime juice, Simple syrup, Mint