Place the joint in a large saucepan and cover with cold water. Add the carrots, onion and bay leaf. Bring to the boil, then simmer gently for 20 minutes per half kg.
While the bacon is cooking place the hoisin sauce, rice wine vinegar, soy sauce, brown sugar and five spice powder in a small saucepan over a medium heat. Bring to the boil then reduce the heat and allow to simmer for a couple of minutes until it becomes syrupy. Stir occasionally. Remove from the heat and set aside to finish later when the bacon is cooked.
Set the oven to Gas Mark 6, 200°C (400°F). Take the joint from the saucepan and transfer to a roasting tin. Score the fat. Brush 3-4 tablespoons. of the sauce over it. Place the plums around the joint and add 100mls of the cooking liquid to the roasting tin to prevent the sauce from burning.
Place the roasting tin in the oven for 30 minutes. Then remove from the oven and allow the bacon to rest while you finish the sauce. Add the plums and liquid from the roasting tin to the sauce you have set aside and bring to the boil, stirring gently so that you don’t break up the plums.