Peel, core and slice the apples thinly. Wash the blackberries. Melt the butter in a pan. Mix the breadcrumbs with cinnamon and sugar and throw into the hot butter. Sprinkle a thin layer of well-stirred crumbs on to the bottom of a lightly greased one and a half pint pie dish. Cover with a layer of apple, then a layer of crumbs. Repeat this twice. Then cover with blackberries, then crumbs, apple and lastly crumbs. Bake at 325°F, 170°C, gas mark 3 for about one hour until the top is golden-brown. Serve with cream or creamy custard.