Heat the oven to 200C / 180C fan / Gas 6 / AGA roasting
Take the lamb out of the fridge at least 1 hour before cooking, it needs to be at room temperature.
Use a sharp knife to make incisions in the meat. Mix the rosemary, thyme, oregano and the lemon zest with the olive oil, salt and pepper and massage into the meat. Season the lamb.
Place the garlic, chilli, fennel and potatoes into a large roasting tray. Drizzle over some olive oil, toss. Place the lamb on top of the veggies. Roast for 45 minutes uncovered until the lamb is starting to brown.
Add in the Noilly Prat and the stock. Continue cooking uncovered for 30 minutes more for rare, 35-40 minutes for medium rare. You may need 5-10 mins less in the roasting oven of the AGA.
Remove the lamb and place somewhere warm to rest for at least 20-30 minutes. Turn down the oven to 180C / 160C fan / Gas 3 / AGA roasting oven with cold plain shelf. Cover the veg with foil, place back in the oven and braise in the roasting juices for another 30 minutes. Remove the foil for the last 10 minutes to crisp up the potatoes.
When ready to serve, place the veggies and juices on a warm serving platter and scatter the fennel fronds, parsley and squeeze half the lemon over the veg, carve the lamb and serve immediately - see below for serving suggestions.