To make the marinade, put the olive oil, cayenne pepper, fresh and ground coriander, cumin, garlic, lemon juice, paprika and parsley in a shallow dish and stir until smooth. Season with salt and pepper to taste.
Cut several slashes in each chicken breast. Add the chicken to the marinade and turn it until it is coated all over, rubbing the marinade into the slashes. Cover and chill for 2 hours.
Put a kettle on to boil. Put the couscous into a pan and pour 300 ml (10 fl oz) of boiling water over it. Cover and leave for 5 minutes to fluff up.
Meanwhile, stir the peaches, raisins, tomatoes, coriander and olive oil into the couscous. Adjust the seasoning to taste, cover and set aside.
Heat the grill to medium. Grill the chicken breasts for 3-4 minutes on each side, until the juices run clear when they are pierced with a knife. Carve them into slices and serve on top of the fruity couscous, garnished with a few sprigs of coriander.