Place all the kefta ingredients in a food processor and pulse several times until well combined. Tip into a large bowl and, using wet hands, shape the mixture into 16 meatballs.
Heat the oil in a large, nonstick frying pan over a medium heat, add the meatballs and then fry for 10–12 minutes, turning frequently, until cooked through and browned all over. Remove with a slotted spoon and drain on kitchen paper.
Meanwhile, wrap the pitta breads in foil and place in a preheated oven, 180°C (350°F), Gas Mark 4, for 5–8 minutes or until warm. To make the salad, mix the carrot, radishes, lettuce and cucumber in a bowl.
Split open the warmed pittas, fill with the salad and then add the meatballs. Squeeze over a little lemon juice and serve immediately.