Mix together the sugar, sultanas, mixed peel, lemon zest and cold tea in a large bowl, cover it with cling film and leave to soak in a cool place for 6 hours, or overnight.
When you are ready to make the teabread, heat the oven to 160°C (325°F, gas mark 3). Line a loaf tin measuring 22 × 11 × 6 cm (8½ × 4¼ × 2½ in) with baking paper.
Stir the egg and flour into the fruit mixture, beating thoroughly, then pour it into the tin and smooth the surface. Bake for 1 hour 15 minutes, or until the loaf has risen, is firm and a skewer inserted in the centre comes out clean.
Leave the loaf in the tin on a wire rack for 2 hours-2 hours 30 minutes to cool completely.
When the loaf is cool, turn it out of the tin, remove the lining paper, then wrap it in greaseproof paper and store in an airtight container for at least one day before slicing. Serve the teabread plain or with your favourite low-fat spread.
Variation: you can use any other distinctive tea for this loaf, including fruit tea.
10 minutes, plus 6 hours, or overnight, soaking, 2 hours 30 minutes cooling and 24 hours maturing