Place the flour, salt and yeast in a large mixing bowl and then rub in the butter using your fingers until the mixture resembles fine breadcrumbs. Mix in the sugar, mixed spice and dried fruit until evenly distributed.
Add the egg and tea and bring the mixture together to form a dough. Knead on a clean work surface until smooth. Place back in the bowl, cover with oiled cling film and leave until doubled in size - at least one hour.
Preheat the oven to 200C/180C fan/400F/Gas 6 and grease a 900g/2lb loaf tin.
Knock back the dough, then shape it and fit it into the loaf tin. Cover again with oiled cling film and prove for a further 30 minutes. Remove the cling film and bake in the centre of the oven for 20 minutes.
Cover the bara brith with aluminium foil and continue to bake for a further 25 minutes. Remove from the oven, turn it out of the tin and leave to cool on a wire rack for 20 minutes.
For the sugar syrup, bring 50ml/1¾fl oz of water and the sugar to the boil in a small saucepan and cook until syrupy. Remove from the heat and brush the loaf with the glaze. Leave to cool completely before cutting. Serve in slices with butter, if you like