0UK units of alcohol (1 unit = 10 ml pure alcohol)
0total liquid, before ice (the glass needs room for ice too)
Drag the lemon and soda, switch gin style. Old Tom gin is sweeter, so the syrup drops to about half, a rule of thumb from drinks writer David Embury. Strength assumes 40% gin and about 20% water gained from shaking; the ice in the glass adds more as it melts.