Preheat your oven to 180C / 160C fan/ gas mark 4 / 350F. Wrap the tortillas in foil to make a sealed parcel and place in the oven when the oven is heated up. Cook for 10 minutes then remove from the oven.
Meanwhile mix together the ingredients for the fajita seasoning. Add the lamb leg steaks and coat thoroughly. (If you have time you can leave the lamb in the marinade for up to 2 hours for extra flavour, but this is optional.)
Next, heat up a griddle pan or frying pan over a high heat for 1 minute. Place the lamb in the pan (set aside the leftover fajita seasoning) and cook for 1 minute on each side, then cook for a further 2 minutes on each side for medium (6 minutes total) or a further 3 minutes on each side for well done (8 minutes total).
When the lamb is ready, place on a board or a plate to rest.
Meanwhile, place another pan over a high heat with the oil. Heat for 1 minute then add the peppers and onions and stir fry for 3-4 minutes, or until well browned. Turn the heat right down and add the remaining fajita seasoning (from the bowl the lamb was in). Fry for 2 more minutes.
Slice the lamb and add it to the pan with the veggies. Sprinkle over a little fresh coriander if you wish and serve at the table with the warm tortillas and all your favourite toppings.
Nutrition information is approximate and meant as a guideline only.