Preheat the oven to 350 degrees F (175 degrees C). Grease and flour an 8x4 inch loaf pan.
In a small saucepan, combine the butter, sugar, golden syrup, and milk. Bring to a boil, then remove from heat, and set aside. Sift the flour, baking soda, ginger, and allspice into a large bowl. Stir in the boiled mixture until just blended. Pour the batter into the prepared pan.
Turn down the oven to 325 degrees F (160 degrees C), and bake for 1 hour, or until the top of the loaf springs back when lightly touched.