Preheat the oven to 190ºC, fan 170ºC, gas 5. Put the apples, pear, lemon zest and juice, raisins, brown sugar and butterscotch pieces in a large bowl and mix together.
Line a baking sheet with baking parchment. Lay a sheet of filo on the lined baking sheet and brush with melted butter. Repeat with the remaining sheets of filo, brushing each with butter. Place the fruit filling along a long edge of the pastry, leaving an inch space at either end. Using the baking parchment to help you, roll the pastry up around the filling, folding in the ends to seal.
Brush the top of the strudel with the remaining butter, then bake for 20 minutes, until crisp and golden. Dust with icing sugar, slice and serve warm.