Rinse the rhubarb well and chop them up into 5cm (2") stalks.
Place everything into a saucepan and bring to a gentle boil on medium heat. No need to skim any surface scum. If you don't boil it vigorously, there will hardly be any.
Lower the heat right down and simmer for 25 - 30 minutes until the rhubarb has fallen apart.
Strain into a sterilised jar or bottle, either using a fine mesh strainer or a muslin cloth lined strainer, as discussed above.
Store in a cool place and use within 2 weeks. If it lasts that long! I tend to keep mine in the fridge, although it's not necessary, given all that sugar!
To serve, just dilute with water, as you would any cordial, at a ratio of 1 syrup:4 water. But this is a matter of taste.