Put the sugar and water into a saucepan, stirring to dissolve the sugar over a medium heat, then bring up to the boil and simmer for two minutes.
Let it cool.Mix the lemon juice with the ginger, add most of the COLD syrup and top up with water to taste.
Add the rest of the syrup if you like.
Add some ice and serve
Roll the limes under your hand on the work surface to soften them, makes juicing them easier