Scrub lemons well and pat dry to remove preservative wax. Peel off the rind avoiding bitter white pith.
Mix lemon peel, juice and vodka in large jar with 500ml water.
Mix the sugar with 125ml water in a small pan and slowly bring to boil to dissolve sugar, allow to cool slightly and then add to the vodka jar.
Cover and set aside for 24 hours in a cool place.
Strain through muslin/cheesecloth or kitchen paper twice to ensure it is completely clear and pour into sterilised bottles.