Remove the skin and fat from the leg of lamb and season with salt. Poke a knife into the meat and insert slivers of garlic in the holes.
Heat the oil in a large frypan over medium-high heat. Place the leg of lamb in the hot frypan and cook until browned all over the outside, turning as needed. Transfer to a large roasting pan. Arrange slices of lemon over the roast and secure with toothpicks.
In a small saucepan combine the water, butter and Worcestershire sauce; bring to a boil. Pour the sauce over the meat and then cover the roasting pan with aluminium foil.
Roast for 2 1/2 hours in the preheated oven, basting every 30 minutes. Remove the aluminium foil and lemon slices and discard. Continue to roast for an additional 30 minutes. Remove from the oven and cover loosely with aluminium foil. Allow it to rest for 15 to 20 minutes before carving.