To make the basic suet pastry, sieve the flour, baking powder and salt together, then rub in the finely chopped suet. Add the water and mix to a dough.
2. Roll out to a rectangle 25 x 15cm and 15 mm thick.
3. Sprinkle with currants and raisins, leaving a border of 1cm (1/2 in) round all sides. Press the fruit in and sprinkle with lemon rind. Paint the borders with water.
4. Turn the two short sides in and seal. Roll up from a long side carefully, to keep all the fruit in. Seal when rolled up.
5. Take a clean tea towel and rinse in boiling water. Sprinkle with flour and shake off the excess. Lay the roll on top of the cloth, fold the cloth over, and fix at the ends with string.
6. Steam the cloth-wrapped roll for 1 1/2 hours. Take out, unwrap, cut into slices and serve with custard or jam sauce.
