Preheat the oven to 200C/400F/Gas 6.
Rub the lamb with the olive oil and season well with salt and freshly ground black pepper.
Heat a small ovenproof frying pan until hot, then place the lamb, garlic and rosemary into the pan and sear for 2-3 minutes on each side.
Transfer the pan to the oven and cook for ten minutes or until cooked but slightly pink in the middle.
Place the lamb onto a plate and cut into four slices, then add all of the remaining ingredients to a bowl and mix well to combine.
To serve, place the mixed salad ingredients onto a serving plate, then place the lamb on top of the salad.