Preheat the oven to 180°C.
Thinly slice two of the garlic cloves, peel & squash the rest. Thickly slice the potatoes.
Make slits all over the lamb, using a sharp knife, then push a slice of garlic and a bit of rosemary into each. Season with salt and pepper and rub some oil all over the meat.
Put the potatoes and garlic cloves into a roasting tray. Drizzle with the olive oil, season and toss. Scatter over the remaining rosemary sprigs. Put the lamb on top and cover loosely with foil.
Roast for 40 minutes, then remove the foil.
Slice the lemon and drain the artichoke hearts. Add these to the potatoes, then cook in the oven for 15 minutes.
Take the tray out of the oven and pour over the stock.
Turn up the temperature to 200°C and roast for a further 20 minutes for medium or longer for well-done.
Remove the tray from the oven and cover the lamb loosely with foil. Let it rest for 15-20 minutes, then carve & serve with the potatoes, artichokes, lemons and the juices.