Measure the water into a small saucepan, sprinkle on the gelatine and set aside to soak for 5 minutes. Then place over low heat and stir until the gelatine has dissolved – do not allow the mixture to boil. Draw the pan off the heat.
Peel the bananas and cut into chunks. Place in a blender, along with the sugar and lemon juice. Cover and blend to a purée. Alternatively, the mixture may b