Sift the flour and salt into a large bowl.
Beat the egg, water and butter together until they are well blended.
Stir the egg and water mixture into the flour and mix well.
Knead with your hands until a firm dough is formed.
Place the dough on a floured board and continue kneading for about 10 minutes until it is smooth and elastic.
Place the dough in a warmed, large mixing bowl.
Cover the bowl and set it in a warm, draught free place for 30 minutes.
Meanwhile, prepare the filling.
In a bowl, combine the cheese, sugar, eggs, salt, lemon rind and sultanas or raisins, beating until they are well blended.
Spread out a large, clean cloth on a table.
Sprinkle with flour.
Place the dough on the cloth and roll out the dough as thinly as possible.
Lift and stretch the dough, pulling the dough until it is paper thin.
This should be done as carefully as possible.
Do not worry if a few small holes appear.
With scissors, trim the outer edges of the dough so that the sides are straight.
Preheat the oven to very hot 450°F (Gas Mark 8, 230°C).
Grease two baking sheets with half the melted butter.
Brush the dough with half the remaining melted butter and sprinkle with nearly all the breadcrumbs.
Spoon the cheese in a long strip on to the dough, 3 inches away from the edges of the sides.
Using the cloth, lift the dough over the filling and roll it up Swiss [jelly] roll style.
Tuck in the ends.
Brush the top with the remaining melted butter and cover with the rest of the breadcrumbs.
With a sharp knife, divide the strudel into pieces long enough to fit the baking sheets.
Place the strudels on the baking sheets with the seams underneath.
Put the baking sheets in the oven and bake for 10 minutes.
Reduce the oven temperature to fairly hot 400°F (Gas Mark 6, 200°C) and bake for a further 20 minutes, or until the strudels are golden brown.