Heat the oven to 200C/180C fan/gas 6. Put the damsons into a pan with the sugar, butter and sloe gin if using (or a splash of water if not) and heat gently until the damsons start to give off their juices. Tip into the base of a large shallow gratin dish (about 25cm long) and stir through the apple slices.

Put all the crumble ingredients into a food processor with a pinch of salt, and using the pulse button, whizz until the mixture just starts to clump together. Don’t whizz for too long or the mixture will stick together too much. Alternatively, rub the butter into the flour using your hands and then stir in the other ingredients.

Scatter the crumble over the damsons and bake in the oven for 30-40 mins until golden brown. Leave for about 15 mins before serving with custard or cream. Remember to warn everyone about the stones!