Preheat the oven to 180 degrees C

Put the flour and butter or margarine into a bowl

Rub the fat into the flour using your fingertips, until it looks like breadcrumbs

Stir in the sugar

Stir in the oats

Peel the apples and slice into chunks

Place in a casserole

Wash the blackberries in cold water and stir into the apples

Sprinkle the sugar over the fruit

Add the water

Spoon the crumble over the top of the fruit, ensuring an even covering

Bake in the preheated oven for about 45 minutes

Serve with custard, ice cream, evaporated milk or cream