Chill the glass

• Fill the highball glass with ice cubes to chill it.

Shake the cocktail

• Fill the shaker with ice.
• Add the gin, lemon juice and simple syrup.
• Shake well until the outside of the shaker feels cold.

Assemble and serve

• Strain the mixture into the chilled glass over fresh ice.
• Top up with the club soda.
• Stir gently and garnish with a lemon slice.