The pastry: sift the flour in to a large bowl. Add the butter and rub in until the mixture resembles to fine bread crumbs.

Stir in the sugar, then add egg and water to make it soft. Wrap in cling film and chill for 30 minutes.

Roll out the pastry on a lightly floured surface. Bake blind in a preheated oven at 200° for 10 minutes until the pastry shell is beginning to brown at the edge. Remove the beans and foil and bake for another 10minutes. Leave to cool.

Baking blind: Prick the pastry shell all over with a fork. Line with a piece of foil, allowing it to come high above the rim so that it can be lifted out easily after baking. Fill the shell with ceramic baking beans or uncooked rice and bake in a preheated oven at 190° for 10 minutes. Remove the beans and foil and bake for another 10 minutes.

Pour two-thirds blueberry pie filling in to the baked pastry shell. Pour cold milk in to a bowl and add instant pudding and beat slowly for one minute on lowest speed in electric mixer until well blended.

Add sour cream and lemon juice to the pudding and mix until well blended. Spread over blueberry filling and top the pudding mixture with remaining blueberry filling. Refrigerate 4 hours before serving.