Heat the oil in a large saucepan then add the chicken and brown on all sides. Remove from the pan.
Reheat the oil, add the garlic, onions and turmeric and cook over a medium heat for 5 minutes, turning from time to time.
Return the chicken to the pan together with the basil, salt and pepper, mix well then add enough water to just cover the chicken. Bring to the boil, stirring, then reduce the heat and simmer for 40 minutes, stirring from time to time and adding a little more water if necessary, until the chicken is very tender.
Add the olives, cilantro, and lemon slices and continue to cook for a further 10 minutes. Serve over couscous.