1. Place the chicken breast-side down on a chopping board. Using poultry shears or strong scissors, cut either side of the backbone and discard. Turn over and cut in half along the centre of the breastbone. Use a pan or rolling pin to beat the chicken halves to flatten slightly.
2. Mix the juice of 1/2 lemon with the remaining ingredients and place in a wide shallow dish.
3. Coat the chicken, cover and place in the fridge to marinate (2 hours minimum). Allow it to come to room temperature just before cooking.
4. Heat a large cast-iron frying pan over a medium heat for 1-2 minutes, then add the chicken halves skin-side down and set the smaller pan on top to weigh them down. Cook for 10 minutes until well browned, turn and cook the other side for 10 minutes.
5. Reduce the heat and pour the marinade over. Add the remaining lemon (cut into quarters) to the pan. Cover and cook for 10 minutes then turn and cook for a further 10 minutes until cooked through in the thickest part of the leg. Serve with the cooking juices and a green salad.