Chop the fruit to your liking and coat with the lemon zest and juice, sugar and flour. Place the fruit in a buttered dish.
In a bowl mix together all the ingredients except the butter. With your hands rub in the butter and form clumps. Spread the clumps all over the fruit, making sure that the fruit is all covered.
Bake the fruit crisp at 170°C for about 45 minutes or until all bubbly and golden.
When ready, let the crisp rest for about 20 minutes so that juices thicken. Whilst still warm serve the fruit crisp in a bowl topped with a generous scoop of ice cream.