Put the sultanas, currants and raisins, mixed dried fruit, mixed peel, brown ale, rum, orange and lemon juices and zests into a large bowl, and stir together. Cover and leave to steep overnight.
The next day, add the remaining ingredients to the bowl, and mix well.
Put a 2-litre/3 1⁄2pt pudding basin on a trivet in a large saucepan with a lid, and pour in enough water to come halfway up the side of the basin. Remove the basin and put the water on to boil.
Brush the basin with melted butter, and line the bottom with baking parchment. Fill with the pudding mixture, then cover with a round of buttered baking parchment. Top with pleated foil, and secure with string around the rim of the basin.
Steam the pudding for 8 hours in the saucepan with the lid on, topping up with boiling water when necessary. Invert the pudding onto a serving plate. Serve hot with brandy sauce, cream or ice cream.