Put the raspberries into the blender with half of the water and mix until smooth on a medium speed. Strain through a fine sieve into a deep bowl.

Put the remaining water into a pan with the sugar and heat, stirring until the sugar dissolves. Allow the syrup to cool.

Stir the syrup into the raspberry purée then pour into a container. Cover and freeze for 45 minutes, then scoop the mixture back into the blender jug and give a few pulses to break up the crystals.

Repeat twice then leave to freeze solid.

About 30 minutes before serving, transfer the sorbet to the refrigerator so the sorbet can be scooped easily.

Alternatively, if you have an ice-cream maker, you can make the sorbet in it without having to blend it during the freezing stages.