Add 12 fresh or frozen blueberries to a Collins glass and crush them with a muddler or the back of a spoon.
Top the glass up with ice and pour in 1½ oz Sipsmith London dry gin, 1½ oz honey syrup and 2 oz lemon juice.
Stir, top with club soda. Garnish with fresh or frozen blueberries skewered on a cocktail pick.
Combine honey and boiling water in a heatproof glass jar. Stir until honey is dissolved. Cool to room temperature before using. Honey syrup will keep refrigerated in an airtight container for 2 weeks.