Preheat oven to 200C/400F/Gas 6. Place three cocktail sticks into a bowl of water to soak for ten minutes.
Place the pork loin between two pieces of cling film. Flatten out the pork with a meat mallet or the end of a rolling pin, until 1cm/¼in thick.
Place the prunes along the centre of the meat, season with salt and freshly ground black pepper and roll up like a cigar. Secure the pork with the soaked cocktail sticks.
Heat the oil in a large ovenproof frying pan. Add the tomato halves, sweet potato and the stuffed pork.
Cook the pork on all sides until golden-brown all over, then transfer the pan with the pork and vegetables to the oven to roast for 8-10 minutes, or until the pork is completely cooked through. When the pork is cooked, remove from the pan and rest for five minutes in a warm place.
Meanwhile, boil the beans in a pot of boiling salted water for 3-4 minutes, until just cooked, then drain.
To serve, slice the pork and arrange the slices on a serving plate with the roasted vegetables and beans alongside.