In a medium bowl, pour 1 cup boiling water over the packages of dry gelatine, stirring to dissolve.
Stir in the juice and 2 cups of ice cubes and refrigerate until the mixture is thick and syrupy.
Stir in the celery, apple and cranberries and pour into a gelatine mould or bundt pan.
Refrigerate for at least 3 hours, or until it’s well set, and invert onto a plate to serve. (If it doesn’t come out, dip the bottom of the mould into a sink of warm water for just a few seconds and try again.)