In a large mixing bowl, combine the raisins, currants, and sultanas. Add the orange zest and juice. Stir and let soak for 10–15 minutes.
Add the suet, flour, mixed spice, breadcrumbs, and brown sugar to the fruit. Mix thoroughly.
Beat the egg lightly and stir it into the mixture. Pour in the ale, rum, and brandy. Mix into a thick, heavy batter.
Grease a pudding basin or stainless steel mixing bowl generously with butter. Spoon in the mixture, pressing gently to remove air pockets.
Cover the basin with foil, securing tightly with string or a rubber band.
Place in a pot with simmering water reaching halfway up the sides of the basin. Steam gently for 3–4 hours, topping up the water as needed.
Remove from the water and allow to cool completely. The pudding may be eaten immediately or wrapped and stored in a cool place for 2–4 weeks to mature.
To serve, reheat by steaming for 1–2 hours, then turn out onto a plate. Optionally flambé with warm brandy before serving.