Put all the dried fruit in a bowl with 100ml rum or brandy. Cover with cling film and leave for 1-2 days to soak, stirring occasionally. Line a 22cm-deep round or 20cm-deep square cake tin with 3 layers of baking paper. Pre-heat the oven to 150C/130C Fan/Gas 2.
Sift the flour and mixed spice together. Cream the butter and sugar together in another large bowl, then beat in the eggs one at a time. Beat well between each addition, adding a tablespoon of flour with each one.
Add the rest of the flour to the bowl along with the orange and lemon zest, the chopped nuts and the soaked, dried fruit, and any remaining soaking liquid. Stir until evenly mixed.
Put the mixture in the tin and level the top. Pat the top with damp fingertips, but don't make it wet – this helps to prevent the top becoming too hard as the cake bakes.
Wrap with brown paper and tie with string. Bake for 2 hours. Reduce the oven to 140C/120C Fan/Gas 1 and cook for 1 hour 30 minutes to 2 hours or until a skewer comes out clean. Cover with a piece of baking paper after 2 hours if it's browning too much.
Cool on a rack but don't remove the baking paper as this helps keep the cake moist when stored. Once cold, store in an airtight box. Every week, pierce with a skewer, drizzle over 1 tbsp rum or brandy, then re-store. Repeat until ready to ice.
When ready to ice, gently heat the apricot jam in a pan until it has thinned slightly. Pass the jam through a sieve then paint the top of sides of the cake with the jam.
Dust a clean, dry work surface and your rolling pin with icing sugar. Gently knead the marzipan to soften it then roll into a circle slightly larger than the cake and approximately 5mm thick. Wrap the marzipan around the rolling pin, lift over the cake then gently place on top, starting at the far edge and unrolling the marzipan over the cake. Smooth the marzipan over the cake, unfolding any pleats with your hands then trim off any excess with a sharp knife.
Brush the marzipan with previously boiled, cooled water.
Re-dust the work surface and rolling pin with icing sugar and roll the regal-ice to a circle slightly larger than the cake and approximately 5mm thick. Wrap the icing around the rolling pin and lift over the cake. Lay the icing over the cake, starting at the back and lowering it down over the front. Smooth it over the cake with the palms of your hands and trim off any excess icing.
The cake is now ready to decorate as you like.
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