Wash your spinach. If you have a vitamix like me you can add the spinach fresh, if you don't, pop it in a colander in the sink and pour a kettleful of boiling water over it. Rinse with cold water to refresh, then squeeze as much liquid out of it as possible before adding to your blender or food processor.
Prepare the rest of the ingredients. Peel the oranges and kiwi fruit, scoop the flesh from the avocado and juice have a lemon.
Pop all of your ingredients into a blender and whizz until smooth. You can add ice if you like.