Method

Turn the oven to fan 200C/ conventional 220C/gas 7.
Heat half the oil in a flameproof roasting tin or ovenproof sauté pan. Brown the lamb for 2 minutes on each side, then lift out of the pan and set aside.
Add the rest of the oil to the pan, add the potatoes, then fry for 4-5 minutes, until starting to brown.
Add the rosemary and garlic, then return the lamb to the pan, too.
Roast in the oven for 20 minutes, then scatter over the tomatoes and drizzle with the balsamic vinegar.
Place back in the oven for 5 minutes, until the tomatoes just begin to split.
Remove from the oven and serve straight from the dish.