Place the glace cherries, mixed peel and almonds in a large bowl with the dried fruit, lemon, orange and vanilla extracts and brandy. Stir well, cover and leave to soak overnight or for at least 12 hours.
Heat the oven to 150°C, fan 130°C, gas mark 2. Grease a deep 18cm square tin or a 20.5cm round tin and line the base and sides with baking paper.
Sieve the flour, salt, mixed spice and cinnamon into a bowl and put to one side. In another large bowl, cream the butter and sugar together until light and fluffy, then mix in the treacle and marmalade.
Add the eggs a little at a time, beating after each addition. If the mixture starts to curdle, add a tablespoon of the flour to stop it split and continue with the eggs.
Fold in the flour and spice mixture until well mixed, then add the soaked fruit and nut mixture. Put the cake mixture into the prepared tin and make a shallow hollow in the centre with the back of a spoon.
Bake on the lowest shelf of the oven for 3-3½ hours or until a skewer comes out clean. Remove from the oven and cool for 15 minutes, then turn upside down on a wire rack to cool.
When cool pierce the cake with a skewer and pour over 3-4 tablespoons of brandy and let it soak into the cake. Repeat this every week until you are ready to ice the cake.
Wrap the cake in a sheet of baking paper and then in foil, and store in a cake tin.
To decorate the cake, place it on a plate or foil board. Brush the cake all over with warmed apricot jam.
Dust your hands and the work surface with a little icing sugar. Shape the marzipan into a ball, then roll out with a rolling pin into a circle large enough to cover the top and sides of the cake (about 34cm depending on the depth of your finished cake - using a piece of string is a good way to measure how much you will need).
Lift the marzipan over your rolling pin and then drape it over the top and sides of the cake, smoothing it out with the palm of your hand. Trim the edge with a knife.
Repeat with the icing, again smoothing out any creases and trimming the edges. .
Re-roll the white icing trimmings and cut out snowflake or star shapes, and decorate with edible lustre powder and silver balls. Use a little bit of water to dampen the back of the shapes and stick on top of the iced cake.
To finish, fasten a pretty Christmassy ribbon around the base of the cake.