Mix lemon, Heritage olive oil, crushed garlic and rosemary together and rub over the Heritage lamb leg joint. Season the joint with salt and pepper.
Cook the lamb following packet instructions. While the lamb is cooking, slice your Heritage mushrooms and drizzle over a little more Heritage olive oil. Drizzle more oil over your asparagus. Pop the veg around the lamb joint, and cook for a further 20 minutes.
Remove from oven. It should be slightly pink in the middle if you like it medium-rare, or brown if you enjoy it more well done - if it’s too pink for you, pop back in the oven for a further 10 minutes and check again.
Enjoy with a side of crispy layered herby potatoes!