Place the rhubarb into a pan with the honey and water. Bring to the boil, then place a lid on the pan and simmer for 10 minutes.
Add in the strawberries and simmer for a further 10 minutes then remove from the heat and stir in the lime juice. Carefully blend the mixture, using a stick blender.
Pass the mixture through a sieve to remove the strawberry seeds, and pour into a freeze-proof container (a bread tin works well).
Freeze for one hour, and then stir. Freeze for a further 2 hours, stirring every 20-30 minutes to break up large chunks of ice.
You can serve at this point. If storing the freezer for another time, take out of the freezer 15 minutes before serving to let it soften slightly.