Take lamb out of fridge at least 1 hour before roasting.

Preheat oven to 240°C/475°F (220°C fan) with oven shelf in the middle.

Rub - Mix rosemary, garlic and olive oil.

Prepare lamb - Place lamb leg in a roasting pan. Coat with the rub using your hands, then sprinkle with the salt and pepper. Place garlic and rosemary sprigs underneath the lamb, garlic cut face up.

Roast lamb leg for 20 minutes. Turn the oven down to 200°C/400°F (180°C fan) and roast for a further 1 hour or until the internal temperature reaches 53°C/127°F for medium rare. Check first at 45 minutes.

Rest - Remove lamb from oven. Transfer lamb to plate, loosely cover with foil and rest for 20 minutes to 1 hour.

Make gravy while lamb is resting - Discard rosemary sprigs. You should have around 4 - 5 tbsp of fat (drippings). If less, add butter. If much more, discard a bit.

Add flour - Place roasting pan on stove over medium heat. When the fat starts to bubble, then add flour. Mix flour in and cook for 1 minute.

Pour in half the beef stock and mix to dissolve sludge in, then add remaining beef stock and mix.

Use a potato masher to mush the garlic to squeeze out the flavour.

Check salt and pepper.

Simmer for a couple of minutes, stirring, until it starts to thicken. Take it off the stove before the gravy is the thickness you want because it will keep thickening.

Strain into a bowl, mushing garlic to squeeze all the liquid out. Then pour into gravy jug and serve with lamb!