Put the tea, sugar, sultanas and citron into a bowl. Cover and leave to soak overnight.
Preheat oven to 180 C / Gas mark 4. Grease and flour an 20cm round cake tin.
Sift the flour into the fruit mixture. Add the egg and beat well.
Pour into the cake tin and bake in preheated oven for 1 hour and 45 minutes or until skewer inserted into centre of cake comes out clean. Leave in the tin for 5 minutes then turn out onto a wire rack to cool.