Place all the dried fruit in a bowl along with the demerara sugar and cover with the black tea. Leave to soak overnight or at least a few hours.
Preheat the oven to 350ºF and lightly grease a 2 lb loaf tin, then line it with baking parchment. Rough chop the walnuts, add them to the fruit and stir well.
Whisk together the eggs and heavy cream, then stir in the fruit. Sift the flour into the mixture and fold together with a large wooden spoon until completely and evenly mixed. Spoon the mixture into the prepared tin and level the top as flat as you can.
Bake in the middle of the oven for 70 - 80 minutes, until the top springs back when lightly pressed. To check if the cake is cooked, insert a clean knife into the center – if it comes out clean, the cake is ready. If not, bake for a further 10 minutes and check once more.
Remove from the oven and allow to cool before removing from the tin and leaving to cool completely on a wire cooling rack. Serve in slices, well buttered,