Preheat the oven to 170C.
Grease and line 20cm cake tin
Put the raisins, dates, sultanas, and currants into a pan with the butter, water and, condensed milk.
Slowly bring to the boil, stir frequently to prevent the mixture from burning. Reduce the heat and simmer for 4 minutes
Pour the mixture from the pan into a bowl and set aside to cool
Mix together the wholemeal flour, plain flour, salt and bicarbonate of soda in a separate bowl
When the fruit and condensed milk mixture has cooled, fold it into the flour with the marmalade Spoon the mixture into the prepared tin
Cover the outside of the tin with a double layer of baking parchment or brown wrapping paper. This will ensure that the cake is baked in the middle without burning the outside.
Bake the cake in the oven for 2 hours 30 minutes, or until the cake is springy to touch and a skewer inserted into the middle comes out clean
Leave the cake to cool for 10 minutes in the tin, then turn out onto a cooling rack.