Line a 25cm tin with approximately two thirds of the short crust pastry. Reserve the trimmings. Chill until ready to use.
Heat the blueberries, 40g of the caster sugar and the lemon juice in a saucepan until the juices begin to run from the fruit.
Mix the corn flour with water, then stir a little of the hot juices from the pan into the corn flour mixture. Stir this mixture back into the pan and continue stirring until thickened. Set aside to cool.
Pre-heat the oven to 350 degrees F.
In a large mixing bowl, combine the eggs, demerara sugar, remaining caster sugar, glucose syrup, cream, butter, oats, fruitcake and vanilla extract. Mix well and stir in the blueberry mixture.
Pour into the prepared pastry case.
Roll out the remaining pastry and cut into long strips about 2cm wide.
Create a lattice on top of the blueberry filling, by laying out the strips of pastry at 2 cm intervals across the pie, turning the pie 90 degrees and adding a second row of pastry strips to form a criss-cross pattern.
Bake in the pre-heated oven for 45 minutes or until browned and set.
Pour the brandy onto the hot pie and set fire to it carefully with a match. Allow the alcohol to burn off.