Preheat the oven to 180C.
Place the diced apple, first lot of sugar and cinnamon, and the water into a pot.
Bring to the boil while stirring and then drop to a low simmer.
Keep stirring until the apples have softened.
Place apples and any syrup into a pie dish.
To make the crumble, using your hands, mix the flour, remaining sugar, butter, and cinnamon until the mixture looks like bread crumbs.
Pour the flour mixture over the apples in an even layer.
Bake the pie for about 30 min.
Serve hot with ice cream and custard.