Remove the meat from the fridge approx. 1 hr. prior to smoking, pat dry.
Mix the ketchup with all the remaining ingredients. Brush the meat with half of the marinade, set aside the remainder of the marinade.
Charcoal/gas/electric grill: Heat the aluminium tray and sawdust over/on a low heat (approx. 150 °C for approx. 5 mins. until it begins to smoke. Move the tray to the edge of the grill. Place the meat on the grill, cover and grill for approx. 1 hr., turning once and brushing with the remainder of the marinade. Remove the meat from the grill, wrap in foil, place on a baking tray.
Roast for approx. 4½ hrs. in the centre of an oven preheated to 140°C. Remove from the oven, allow to rest for approx. 15 mins., remove from the foil, pull away the meat using two forks.