Add a sprig of rosemary, then gently squeeze a wedge of fresh pink grapefruit into your balloon glass before dropping it in. Add Bombay Sapphire Gin and swirl so the flavours subtly infuse. Fully fill the glass with cubed ice and top with chilled tonic water. Gently stir to combine and finish the drink with a wedge of pink grapefruit and sprig of rosemary before serving.