This recipe is based off an old traditional method from coastal south Wales of cooking a Christmas pudding boiled in a linen bag in one lump; hence the name pwdin lwmp nadolig (Christmas lump pudding). Try the old version if you have a cauldron and a spare pillowcase to hand... but I prefer to make it the modern way with a few modern ingredients.
On Christmas Day, boil the pudding for a further 2 hours to reheat.
If you put small coins in the mixture, always warn your guests before they get stuck in.