Start preparing the fruit at least the day before you want to bake the cake.Mix all of the dried fruits together in a large bowl that has a lid, add the rum, stir well, then cover and leave overnight (or for up to a week - give it an occasional stir).
The following day, preheat the oven to 140°C/120°C fan/275°F/gas mark 1. Grease a deep 20cm/8inch round cake tin and line it with a double layer of baking parchment.
In a large bowl, whisk together the dairy free margarine (or softened coconut oil), dark and light brown sugars, treacle and orange and lemon zest until fluffy.
In a separate bowl, sift together the plain flour, ground almonds, bicarbonate of soda, mixed spice, cinnamon and nutmeg.
Tip the dry ingredients into the margarine mix, along with the soy milk and red wine vinegar. Stir until just combined; be careful not to over-mix. The batter should be very thick. If it is really dry you can add a drop more milk but be careful not to add too much, the batter should be stiff.
Stir in the soaked dried fruits, along with any leftover liquid, and the chopped almonds.
Scrape the batter into the prepared tin and use a spatula to spread it level. Because it is so thick it doesn't spread much in the oven so it is important that you get it as even as you can.
Bake for 2-3 ½ hours until a skewer inserted into the centre comes out clean; mine took 2 ½ hours. Leave the cake to cool completely in the tin on a wire rack then turn it out and brush all over with rum or brandy.
Wrap the cake up in baking parchment then tin foil (it MUST be completely cold first), and store in an airtight container, feeding every week or two with rum or brandy, for up to three months.