Tip the raisins, currants and sultanas into a bowl. Pour over 200ml ginger wine, then cover and leave to sit at room temperature overnight so that the fruit plumps up.
Heat oven to 160C/fan 140C/gas 3. Using the bottom of a 20cm, loose-bottomed cake tin as a template, cut out 2 circles of baking parchment. Then cut 2 thick strips (about 2cm deeper than the tin) that will fit around the inside of the tin. Make small cuts along one of the edges, about 2cm apart. Grease the tin, then place one parchment circle at the bottom. Place one strip inside the tin, making sure the cut side is at the bottom, as this will help you to fit it inside. Do the same with the remaining strip, then place the second circle on top (see step-by-step).
Put the butter and sugar into a mixing bowl and whisk with an electric beater until creamy and light, about 5 mins. Add the eggs, one at a time, making sure you stir well after each addition, then mix through the flour, ground almonds and spices. Stir in the soaked fruits, and any liquid left over, with the fresh root ginger and treacle until everything is well combined.
Spoon in the mixture and smooth the top, then use a spoon to make a slight dip in the centre. This will ensure the cake has an even surface when finished. Bake for 30 mins, then lower the oven to 150C/fan 130C/gas 2 and bake for another 2 hrs until a skewer inserted in the middle comes out clean. Skewer the cake all over, then drizzle over the remaining 4 tbsp ginger wine. Leave the cake to cool in the tin, then peel off the lining paper. To store, wrap first in baking parchment and then in tin foil. The cake will keep in a cupboard for up to 3 months or can be frozen for up to 6 months.