Steep tea leaves in hot water for 10 minutes then strain. Add the plum jam, mix well and set aside.
Dice two of the plums and halve the remaining four plums. Mix the diced plums, sausagemeat, breadcrumbs, onion, cinnamon and garlic in a large bowl until well blended.
Cut each pork tenderloin lengthwise, ¾ of the way through. Open up and flatten with a meat mallet to 1½ cm thickness. Spread half of the plum stuffing evenly onto each pork tenderloin, leaving a ½cm edge of meat. Roll pork tightly. Tie with kitchen string at 2½ cm intervals. Place pork tenderloins in a shallow baking pan that has been lined with foil. Arrange halved plums around the pork.
Roast in a preheated 350°F (180°C, Gas Mark 4) oven for 40 to 50 minutes or until pork is cooked as desired. Brush with plum jam mixture during the last 20 minutes of cooking. Let stand for 5 minutes before slicing and serving.
