Preheat the oven to 180 degrees C (if using a fan forced oven 170 degrees C). Line a 28cm by 18cm baking tin with baking paper.
Mix flour, sugar, ginger and bicarb soda together in a bowl. Using your fingers, rub the margarine in until the mixture resembles breadcrumbs. Add the beaten egg, syrup and hot water and mix well with a wooden spoon until combined.
Pour the mixture into the prepared tin and bake in the middle of the oven for 35 to 40 minutes, or until golden brown and the top is springy to the touch. Leave to cool in the tin. Once cool, cut into squares.
Mixture will look glossy and kind of runny. This is what you want. Can be served as a dessert with custard.