1 Heat the oven to 200°C (180°C in a fan oven), 400°F, gas 6 and brush a rectangular baking tin (approx 20 x 30 cm) with butter.
2 Mix together the flour, cinnamon and sugar and sieve into a bowl. Melt the butter in a small pan and slowly add to the flour mixture. Stir with a fork to make small clumps.
3 Mix in 2/3 of the nuts. Place half of the crumble mixture in the baking tin and press down gently. Spread the berries over the crumble, then spread the remaining crumble loosely over the top.
4 Cook in the oven for 25-30 minutes until golden brown. Serve warm or cold, sprinkled with the remaining nuts.