500ml good quality gin or vodka (we like Tanqueray or Sipsmith gin, or Chase or Grey Goose vodka)
Divide the vermouth among 4 martini glasses, swirl it round each glass so they’re coated, then tip the excess into a jug. Put the glasses in the freezer until needed. Pour the vodka or gin into the jug with the vermouth, stir with a long spoon to combine, then cover and freeze for at least 1 hour or overnight.
To serve, take the glasses out of the freezer and pour the cocktail equally among them. Garnish each with a good quality green olive and it’s a wrap.