Mix flour, butter, sugar, salt and egg together until it forms a ball. Place in fridge for 30mintues (or overnight). Press into prepared (with flour & oil) round tart pan, no larger than 27cm diameter (the dough may need kneading if left in the fridge overnight). Spread marmelade on top. Bake at 180C (350F) for 35minutes or until crust is light golden colour. Cool before serving.