Preheat the oven to 170C/325F/gas mark 3. Grease an approx 22x11cm (8.5x4in) loaf tin and line with a strip of baking parchment.
Cream the butter, sugar, golden syrup and treacle together until light and fluffy. In a separate bowl, sift together the flour, ground ginger and cinnamon.
Beat the eggs into the butter mixture one at a time, whisking well after each addition and adding a heaped tablespoon of the flour mix with each one. Add the rest of the flour along with the milk and salt and mix until just combined. Finally fold in the diced apple.
Scrape the mixture into the prepared tin and level the top. Arrange the sliced apple in a row along the middle of the loaf. Bake for 1 to 1 ½ hours until a skewer inserted into the center comes out clean; cover the top of the loaf with foil after about 40 minutes to prevent it from getting too dark.
Leave to cool in the tin for about half an hour then carefully turn out onto a wire rack and leave to cool completely.
To make the toffee topping, place the toffees and milk in a small saucepan over a low heat. Stir until the toffees have melted and the sauce is smooth, add a drop more milk if it is too thick to drizzle.
Drizzle the sauce all over the cake and serve. The cake will keep well in an airtight container for up to a week, though the toffee sauce will lose it's shine.