Dissolve the sugar in the water and boil for 3-4 minutes.
Heat the redcurrants gently until the juices run out. Squash with a wooden spoon. Remove from heat and add the orange and lemon juice.
Purée the raspberries in a blender and then push through a wire sieve, using a soup ladle, followed by the redcurrants with all the juices. Add the syrup and chill thoroughly, preferably overnight.
Place the mixture into a large shallow container, preferably metal, and place in deep freeze. Whisk at least 3 times while freezing. When nearly frozen, pack into the plastic container and seal.
© 1984 All rights reserved. Published by Jon Croft.