Crush ice by putting in a bag and placing a towel over it and smashing with a rolling pin. Add a generous amount to the glass with the sherbet.
Pour in the vodka and gin and stir well.
Top off with a splash of soda water.
Squeeze over the lime juice and drop the wedges into the glass. Serve.
To make your own lemon sorbet put 250ml water into a pan with 400g caster sugar. Heat and stir until clear, then add the juice of 6 lemons and stir. Leave till cool, then transfer to a container and freeze, stirring occasionally.