½ pint Water
550g Preserving sugar (you can buy this in Waitrose)
1no Lemon juice
Put the washed berries into a thick bottomed pan and add the water. Simmer slowly over a low heat until the blackcurrants are very soft.
Add the sugar and stir over a low heat until the sugar has dissolved then boil rapidly until setting point is reached (you can test this by placing a small amount of the jam in the centre of a cold plate and it should set on no water runs over the plate).
Add the juice of one lemon and stir for one minute.
Spoon the jam into hot jars and seal down.