Sift the flour and spices into a large bowl, then mix the bicarbonate of soda with the milk and set it on one side.
Now measure the black treacle, golden syrup, sugar and butter into a saucepan with 75ml of water, heat and gently stir until thoroughly melted and blended – don’t let it come anywhere near the boil and don’t go off and leave it!
Next add the syrup mixture to the flour and spices, beating vigorously with a wooden spoon, and when the mixture is smooth, beat in the egg a little at a time, followed by the bicarbonate of soda and milk.
Now pour the mixture into the prepared tin and bake on a lower shelf so that the top of the tin is aligned with the centre of the oven for 1¼–1½ hours until it’s well-risen and firm to the touch.
Remove the cake from the oven and allow to cool in the tin for 5 minutes before turning out.
If possible, store it in a cake tin, still in its lining, for 24 hours before eating, and serve it cut in thick slices spread with butter.