Put two martini glasses in the fridge to chill. Thread the olives onto two cocktail sticks and set aside.

Fill a jug or mixing glass with the ice, then pour in the gin, vermouth and olive brine. Stir until the outside of the jug feels cold. Taste to make sure that it's icy cold and that you’re happy with the dilution.

Strain the mix into the chilled glasses and garnish with the olive skewers.