Put the redcurrants and sugar in a heavy-based saucepan and cook over a low heat, stirring occasionally, for 10–15 minutes until tender. Add the strawberries and raspberries, remove from the heat and leave to cool. Strain the fruit, reserving the juice.
Cut 3 rounds of bread the same diameter as a 900 ml (1½ pint) pudding basin. Shape the remaining bread to fit around the side of the basin. Soak all the bread in the reserved fruit juice.
Line the base of the basin with one of the rounds, then arrange the shaped bread around the side. Pour in half the fruit and place another round of bread on top. Cover with the remaining fruit, then top with the remaining bread round.
Cover with a saucer small enough to fit inside the basin and put a 500 g (1 lb) weight on top. Chill in the refrigerator overnight.
Turn out on to a serving plate, pour over any remaining fruit juice and decorate with a few reducurrant sprigs arranged on top of the pudding in the centre, if wished. Serve with whipped or pouring cream.