Soak fruit in tea:

In a large glass bowl, combine the mixed dried fruit and caster sugar. Pour the hot, strong black tea over the mixture and stir with a wooden spoon until the sugar is fully dissolved and the fruit is evenly coated. Cover the bowl tightly with plastic wrap or a clean tea towel and allow it to soak at room temperature for at least 6 hours, ideally overnight, until the fruit has plumped and absorbed nearly all the liquid.

Preheat oven and prep pan:

Preheat the oven to 325°F (165°C) and position a rack in the center. Lightly grease a 2 lb (900g) loaf pan with oil and line the bottom and sides with a long strip of parchment paper, leaving an overhang on the long edges to facilitate lifting the cake out later.

Mix batter with flour and egg:

To the bowl containing the soaked fruit and any residual tea, add the self-raising flour and mixed spice. Fold the mixture using a large metal spoon until no streaks of flour remain. Add the beaten egg and stir until the batter is smooth and glossy, being careful not to overmix.

Bake loaf until done:

Transfer the batter into the prepared loaf pan, spreading it evenly. Bake for 1 to 1 1/4 hours, until the top is dark golden brown and firm to the touch, and a wooden skewer inserted in the center comes out clean.

Cool loaf completely:

Allow the loaf to cool in the pan for 10 minutes, then lift it out using the parchment paper and place it on a wire rack. Remove the paper and let it cool completely before slicing.