Finely grate the rind of the lemons into a bowl. Squeeze the lemon juice (at least 180ml) into the bowl and add sugar and water. Stir well and leave for 1-2 hours in a cool place, stirring occasionally, until the sugar has dissolved. Chill.

Pour mixture into an ice cream maker and process, or pour it into a freezer container and use the good-old hand-mixing method.

When sorbet is firm freeze it in a freezer container for 15-20 minutes or until ready to serve. If necessary, transfer it to the refrigerator 10 minutes before serving to soften.

This sorbet will not be good if frozen for longer than 2-3 weeks.