First cook the apples for a few minutes in a saucepan with the lemon juice, sugar and a tbsp or so of water, until the apples are beginning to soften. Remove from the heat and tip everything into an ovenproof dish, then top with the brambles and berries.
For the crumble, mix the flour and oats and rub in the butter. Stir in the nuts and sugars. Tip over the fruit in the dish and pat dow