Preheat the oven to 300˚F.
Drizzle some oil in a heavy ovenproof pot or Dutch oven set over medium-high heat and brown the roast on all sides, sprinkling with salt and pepper.
Add enough stock to come a bit more than halfway up the side of the meat, add the tomato paste and rosemary or thyme, cover and cook for 3 hours.
Add the potatoes and carrots and return to the oven for another 1/2-1 hour, until the meat is very tender.
Serve carved or pulled apart, with the vegetables and gravy.