Put the sugar and 250ml / 8fl oz (1 cup) water in a heavy - based pan over low heat.
Heat gently, stirring until the sugar dissolves completely.
Increase the heat and bring the syrup to the boil without stirring.
When it comes to the boil, add the milk mixed with 1 teaspoon water. The scum will rise to the surface.
Boil for about 10 minutes.
Then strain the syrup through a piece of muslin (cheesecloth). Do not squeeze the muslin.
Meanwhile, rinse the pan.
Return the syrup to the pan and bring to the boil once more.
Add the lime juice. This prevents crystallization of the syrup.
In case more scum rises to the surface, remove it with a slotted spoon.
To test, take some syrup between your thumb and forefinger (index finger).
Be careful, as the syrup is very hot.
Draw your fingers slightly apart. The syrup will form fine threads. The number of thread it forms, will give you the correct consistency.