Put the bay leaves in a saucepan, add 350ml water and the golden caster sugar, bring to the boil, then leave to cool completely. Remove and discard the bay leaves. Chop the lemon into chunks and put in a blender. Add the blackberries (fresh or defrosted) and the bay leaf infusion, blend until smooth, then strain through a sieve into a jug to remove any pith and pips. Serve in tumblers or wine glasses topped up with the sparkling water. Stuff lychees with green olives and skewer onto cocktail sticks to garnish the drink, if you like.