1. Peel, core, and slice the apples.
2. Cook with the brown sugar, water, and lemon rind in a covered pan until soft.
3. Fill a greased 1 litre pie dish with the apples.
4. Rub the fat into the flour until it resembles fine breadcrumbs.
5. Add the caster sugar and ginger and stir well, sprinkle the mixture over the apples, and press down lightly.
6. Bake in a moderate oven at 180°C, Gas 4, for 30-40 minutes until the crumble is golden-brown.