Preheat the oven to 180°C (350°F) (160°C/325°F fan-forced).

In a large bowl (or on a plate/chopping board), marinate the lamb in the garlic, rosemary, oregano, salt, pepper and olive oil. Use your hands to ensure the lamb is evenly coated on all sides.

Place the onion, carrot, water and white wine in a lidded roasting pan or dish. Rest the marinated lamb on top of the vegetables, along with any of the residual marinade in the bowl. Cover with the lid (or, if using a regular baking dish, cover tightly with a double layer of foil) and roast for 4 hours.

You should be able to pull the lamb apart easily with two forks when it is done. If not, re-cover it and return to the oven until tender (see note 3).

Remove the lamb from the oven. Carefully lift the lamb from the roasting pan, using two sets of tongs (as it will fall apart easily). Place it on a plate or chopping board, cover it loosely with foil and allow to rest for at least 15 minutes.

To make the gravy, place the roasting pan on the stovetop (you may need to transfer the contents into a flameproof pan). Bring to a simmer over medium heat.

Whisk in the flour (it’s okay if lumps form) and, once dissolved, pour in the beef stock. Cook, whisking, for 3–4 minutes, or until the gravy is thick. Season with salt and pepper to taste. Pass the gravy through a sieve, pressing as much of the vegetables through the sieve using the back of a spoon (I like to do this into a large measuring jug, but you could use a large bowl too). You’ll be left with a thick gravy.

Serve with rosemary sprigs and roasted potatoes or a leafy salad, if desired.