Toss the bananas in the lemon juice then place in a large bowl with the peach slices and blueberries. Mix the sugar, breadcrumbs and cinnamon in a small bowl then gently mix with the fruit.
Unfold the pastry sheets, put one in front of you with the longest edge nearest you.
Cut in half to make 2 rectangles, 23 x 25 cm (9 x 10 inches). Put 2 heaped spoonfuls of the fruit mixture on each then fold in the sides, brush the pastry with a little of the melted butter then roll up like a parcel. Repeat to make 8 mini strudels using 4 sheets of pastry.
Brush the strudels with a little more melted butter. Cut the remaining pastry sheets into wide strips then wrap them like bandages around the strudels, covering any tears or splits in the pastry. Place on an ungreased baking sheet and brush with the remaining butter.
Bake in a preheated oven, 190°C (375°F), Gas Mark 5, for 15–18 minutes until golden brown and crisp. Leave to cool on the baking sheet then dust with a little sifted icing sugar and arrange on a serving plate. These are best eaten on the day they are made.