Heat all the ingredients gently in a saucepan, and stir until the sugar has quite dissolved. Bring to the boil and boil briskly, removing the lemon rind after a few moments. Continue boiling until the mixture cracks and is very brittle when a little is dropped into cold water. Remove from heat and allow to cool slightly. Oil a large shallow tin and roll the mixture into long thin strips. Twist and leave to set. Store in airtight containers.