Preheat the oven to 180°C.
Peel & core the pears, cut them into rough pieces. Scatter these into a buttered baking dish together with the blackberries. Squeeze the lemon juice over and sprinkle with half of the sugar.
In a large bowl rub the flour and butter with your fingers until the mixture resembles coarse breadcrumbs. Add the sugar, oats and dried fruit, nuts and chopped, seeds. Combine well, then sprinkle this mixture evenly over the fruits. Make sure the fruits are well covered - you can slightly press down the crumble.
Cook in the oven for 25-30 minutes until golden.
Let it rest for a few minutes, then serve warm.